eeschema: double click on a child-sheet box does not open it anymore

Double-clicking on a hierarchical sheet it does not open it anymore

I don't know if this is the new intended behaviour, so I report it as a bug.

To reproduce the behaviour:
- Create a new project (or open an existing one)
- add a hierarchical sheet
- double click it. Instead of opening the child schematic it just selects the box.

If this behaviour is intended... Double clicking was a very quick way to navigate complex tree-organized schematics, so... I miss that feature.

Cheers,
Dino.

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Tested on revision: 418bd283476353861b122c961fcc086398418db5

Application: Eeschema
Version: (5.1.0-1026-g418bd2834), release build
Libraries:
    wxWidgets 3.0.2
    libcurl/7.52.1 OpenSSL/1.0.2r zlib/1.2.8 libidn2/0.16 libpsl/0.17.0 (+libidn2/0.16) libssh2/1.7.0 nghttp2/1.18.1 librtmp/2.3
Platform: Linux 4.9.0-8-amd64 x86_64, 64 bit, Little endian, wxGTK
Build Info:
    wxWidgets: 3.0.2 (wchar_t,wx containers,compatible with 2.8) GTK+ 2.24
    Boost: 1.69.0
    OpenCASCADE Community Edition: 6.8.0
    Curl: 7.52.1
    Compiler: GCC 6.3.0 with C++ ABI 1010

Build settings:
    KICAD_SCRIPTING=ON
    KICAD_SCRIPTING_MODULES=ON
    KICAD_SCRIPTING_PYTHON3=OFF
    KICAD_SCRIPTING_WXPYTHON=ON
    KICAD_SCRIPTING_WXPYTHON_PHOENIX=OFF
    KICAD_SCRIPTING_ACTION_MENU=ON
    BUILD_GITHUB_PLUGIN=ON
    KICAD_USE_OCE=ON
    KICAD_USE_OCC=OFF
    KICAD_SPICE=ON