UCLabel as ListView delegate crashes while being destroyed

This is causing pay-ui to crash on exit every time (after updating all imports to 1.3).

How can this be reproduced? Preferably without buying something ;-)

Apps can be "purchased" without paying by using the staging store:

* Enable use of the staging server:
   - Log in to the phone with "phablet-shell" and run /usr/lib/*/pay-service/setup-staging.sh

* Search for "delta" in the Ubuntu Store

* Purchase delta

* Use Testing Credit Card
   - Visa: 4111 1111 1111 1111
   - Expiration Date must be a valid date in the future (use the mmyy format).

Having silo 64 installed, I used another way to test:
ubuntu-app-test /usr/lib/payui/pay-ui purchase://com.zeptolab.cuttherope.full

And I'm seeing a bunch of these:
2016-03-22 17:05:03,006 - WARNING - file:///usr/lib/arm-linux-gnueabihf/qt5/qml/Ubuntu/Components/Themes/Ambiance/1.3/ToolbarButtonStyle.qml:57: TypeError: Cannot read property 'overlayText' of undefined

It doesn't seem to crash here.

As we discussed in IRC, the bits from Comment #4 are from the old pay-ui that's still on the image, not the pay-ui from the silo that includes the switch to uitk 1.3.

For the record, how I finally reproduced the crash.
On the phone, with Silo 64 *correctly* installed, which at the time of #4 was not the case:

QML2_IMPORT_PATH=:/usr/lib/arm-linux-gnueabihf/payui ubuntu-app-test gdb --batch -ex 'handle SIGILL nostop' -ex run -ex bt --args qmlscene /usr/share/payui/qml/payui.qml purchase://com.zeptolab.cuttherope.full

On the desktop, with account-plugin-ubuntuone installed and https://code.launchpad.net/~dobey/pay-service/payui-uitk1.3/+merge/289421 applied (works with the pay-service package, no full local build required):

QML2_IMPORT_PATH=$QML2_IMPORT_PATH:/usr/lib/x86_64-linux-gnu/payui gdb --batch -ex 'handle SIGILL nostop' -ex run -ex bt --args qmlscene /usr/share/payui/qml/payui.qml purchase://com.zeptolab.cuttherope.full

The attached snippet is a standalone test case for the crash.

Status changed to 'Confirmed' because the bug affects multiple users.

This bug was fixed in the package ubuntu-ui-toolkit 1.3.1918+15.04.20160404-0ubuntu1 in https://launchpad.net/~ci-train-ppa-service/+archive/ubuntu/stable-phone-overlay

---------------

ubuntu-ui-toolkit (1.3.1918+15.04.20160404-0ubuntu1) vivid; urgency=medium

  [ Benjamin Zeller ]
  * Register expected warning messages in the tree testcase.
  * Add testsuite for Tree. Fixes LP: #1549171.
  * Compile with Qt 5.6. Fixes LP: #1540356
  * More Qt 5.6 fixes.

  [ Michael Terry ]
  * Add grabGesture field to SwipeArea.
  * This field controls whether the SwipeArea takes ownership of the gestures it
    observes. Fixes LP: #1527387.

  [ Timo Jyrinki ]
  * Add a test for blocking if packaging not sorted and clean.
  * More package name transitioning, wrap and sort, fix debian/copyright syntax,
    update standards-version, fix devel package sections and add/fix
    lintian-overrides.

  [ Olivier Tilloy ]
  * Fix dependencies of the transitional dummy package
    qtdeclarative5-ubuntu-ui-toolkit-plugin. Fixes LP: #1553551.

  [ Christian Dywan ]
  * Rename qtdeclarative5-*-plugin to qml-module-*. Fixes LP: #1342031.
  * Require a qtdeclarative5 known to have the tab fence patch.
  * Reset previous theme version and use UbuntuTestCase in tst_animator.
  * BottomEdge(Hint) focus and close via keyboard. Fixes LP: #1523825
  * Add 1.3 version of UbuntuTestCase.
  * No gdb when running unit tests on armv7l.
  * Build-depend on python3-debian for wrap-and-sort.

  [ XiaoGuo Liu ]
  * Fix AdaptivePageLayout documentation.

  [ Tim Peeters ]
  * Properly disable left/right arrows on sections when at the beginning/end of
    the list. Fixes LP: #1551356.
  * Sections and old AppHeader landscape mode. Fixes LP: #1551341.
  * Set the window color as soon as the window is available, to avoid a
    flickering background when it is updated later.
    Fixes LP: #1439133, LP: #1554897
  * Add theme, style and styleName properties to Dialog and Popover.
    Fixes LP: #1555548
  * Update the gallery script to use the new name of the export script.
  * Export the full list of library paths.
  * Prevent Page geometry changes in APL when changing Pages in a column.
  * Fix typo in DatePickerStyle. Fixes: LP #1561440.

  [ Zsombor Egri ]
  * ListItem focus navigation in ListView and other views.
    Fixes LP: #1523815, LP: #1536679, LP: #1549733, LP: #1549743
  * BorromEdge.preloadContent. Fixes LP: #1540454.
  * Asynchronous loader (AsyncLoader) using incubator, prerequisite for
    BottomEdge preloading its content. Fixes LP: #1540454.
  * ListView proxy should not consume up/down key events. Fixes LP: #1554447
  * Pick up the right style. Fixes LP: #1555797
  * Label makes sure the color alteration is known by the theming.
    Fixes LP: #1555784
  * Fix AsyncLoader tests so they create slightly less amount of elements.
  * AdaptivePageLayout removes all pages pushed to next columns when
    addPageToNextColumn() is called. Fixes LP: #1544745
  * Fix BottomEdge content discarding.
  * Disconnect enabled signal in Label in destructor, so functor call will not
    be handled when QQuickItem triggers enabled change. Fixes LP: #1560044.

  [ Andrea Bernabei ]
  * UI G...

This bug was fixed in the package ubuntu-ui-toolkit - 1.3.1918+16.04.20160404-0ubuntu1

---------------
ubuntu-ui-toolkit (1.3.1918+16.04.20160404-0ubuntu1) xenial; urgency=medium

  [ Benjamin Zeller ]
  * Register expected warning messages in the tree testcase.
  * Add testsuite for Tree. Fixes LP: #1549171.
  * Compile with Qt 5.6. Fixes LP: #1540356
  * More Qt 5.6 fixes.

  [ Michael Terry ]
  * Add grabGesture field to SwipeArea.
  * This field controls whether the SwipeArea takes ownership of the gestures it
    observes. Fixes LP: #1527387.

  [ Timo Jyrinki ]
  * Add additional Breaks as requested by archive admin.
  * Add a test for blocking if packaging not sorted and clean.
  * More package name transitioning, wrap and sort, fix debian/copyright syntax,
    update standards-version, fix devel package sections and add/fix
    lintian-overrides.

  [ Olivier Tilloy ]
  * Fix dependencies of the transitional dummy package
    qtdeclarative5-ubuntu-ui-toolkit-plugin. Fixes LP: #1553551.

  [ Christian Dywan ]
  * Rename qtdeclarative5-*-plugin to qml-module-*. Fixes LP: #1342031.
  * Require a qtdeclarative5 known to have the tab fence patch.
  * Reset previous theme version and use UbuntuTestCase in tst_animator.
  * BottomEdge(Hint) focus and close via keyboard. Fixes LP: #1523825
  * Add 1.3 version of UbuntuTestCase.
  * No gdb when running unit tests on armv7l.
  * Build-depend on python3-debian for wrap-and-sort.

  [ XiaoGuo Liu ]
  * Fix AdaptivePageLayout documentation.

  [ Tim Peeters ]
  * Properly disable left/right arrows on sections when at the beginning/end of
    the list. Fixes LP: #1551356.
  * Sections and old AppHeader landscape mode. Fixes LP: #1551341.
  * Set the window color as soon as the window is available, to avoid a
    flickering background when it is updated later.
    Fixes LP: #1439133, LP: #1554897
  * Add theme, style and styleName properties to Dialog and Popover.
    Fixes LP: #1555548
  * Update the gallery script to use the new name of the export script.
  * Export the full list of library paths.
  * Prevent Page geometry changes in APL when changing Pages in a column.
  * Fix typo in DatePickerStyle. Fixes: LP #1561440.

  [ Zsombor Egri ]
  * ListItem focus navigation in ListView and other views.
    Fixes LP: #1523815, LP: #1536679, LP: #1549733, LP: #1549743
  * BorromEdge.preloadContent. Fixes LP: #1540454.
  * Asynchronous loader (AsyncLoader) using incubator, prerequisite for
    BottomEdge preloading its content. Fixes LP: #1540454.
  * ListView proxy should not consume up/down key events. Fixes LP: #1554447
  * Pick up the right style. Fixes LP: #1555797
  * Label makes sure the color alteration is known by the theming.
    Fixes LP: #1555784
  * Fix AsyncLoader tests so they create slightly less amount of elements.
  * AdaptivePageLayout removes all pages pushed to next columns when
    addPageToNextColumn() is called. Fixes LP: #1544745
  * Fix BottomEdge content discarding.
  * Disconnect enabled signal in Label in destructor, so functor call will not
    be handled when QQuickItem triggers enabled change. Fixes LP: #1560044.

  [ Andrea Bernabei ]
  * UI Gallery: fix vertical alig...