Canceling upload of problem information causes dialog to freeze

Canceling the upload of problem information after sending information acquired with `ubuntu-bug [package name]` causes the upload dialog to become unresponsive.

ProblemType: Bug
DistroRelease: Ubuntu 15.10
Package: apport-gtk 2.19.1-0ubuntu5
Uname: Linux 4.3.3-040303-generic x86_64
NonfreeKernelModules: zfs zunicode zcommon znvpair zavl
ApportLog:

ApportVersion: 2.19.1-0ubuntu5
Architecture: amd64
CrashReports:
 640:0:152:907688:2016-01-15 16:04:48.503047587 +0100:2016-01-15 16:04:46.731001423 +0100:/var/crash/_usr_sbin_winbindd.0.crash
 644:0:152:0:2016-01-15 16:04:48.503047587 +0100:2016-01-15 16:04:48.503047587 +0100:/var/crash/_usr_sbin_winbindd.0.upload
 640:163:152:42761293:2016-01-23 03:37:42.503584063 +0100:2016-01-23 03:37:14.182860515 +0100:/var/crash/_usr_bin_rtorrent.163.crash
 644:163:152:0:2016-01-23 03:37:18.986983255 +0100:2016-01-23 03:37:18.986983255 +0100:/var/crash/_usr_bin_rtorrent.163.upload
Date: Sat Jan 23 04:45:02 2016
InstallationDate: Installed on 2015-04-20 (277 days ago)
InstallationMedia: Ubuntu-Server 14.10 "Utopic Unicorn" - Release amd64 (20141022.2)
PackageArchitecture: all
SourcePackage: apport
UpgradeStatus: Upgraded to wily on 2015-10-26 (88 days ago)