QmlDesigner: Fix crash on exit
QmlDesigner: Fix crash on exit

QtCreator crashed on exit when the library/navigator/sidebar wasn't
visible in the Design mode. This is caused by a double deletion: The
widgets have the DesignModeWidget as the default parent + the side bar
items try to delete them on exit.

Fixed by removing default parent.

Task-number: QTCREATORBUG-1197
Reviewed-by: Christiaan Janssen

kuba1/qtcreator,renatofilho/QtCreator,farseerri/git_code,xianian/qt-creator,renatofilho/QtCreator,dmik/qt-creator-os2,amyvmiwei/qt-creator,danimo/qt-creator,malikcjm/qtcreator,dmik/qt-creator-os2,amyvmiwei/qt-creator,ostash/qt-creator-i18n-uk,xianian/qt-creator,martyone/sailfish-qtcreator,sandsmark/qtcreator-minimap,amyvmiwei/qt-creator,KDE/android-qt-creator,richardmg/qtcreator,darksylinc/qt-creator,sandsmark/qtcreator-minimap,Distrotech/qtcreator,omniacreator/qtcreator,colede/qtcreator,richardmg/qtcreator,xianian/qt-creator,bakaiadam/collaborative_qt_creator,xianian/qt-creator,KDE/android-qt-creator,farseerri/git_code,farseerri/git_code,omniacreator/qtcreator,jonnor/qt-creator,ostash/qt-creator-i18n-uk,malikcjm/qtcreator,malikcjm/qtcreator,colede/qtcreator,malikcjm/qtcreator,danimo/qt-creator,martyone/sailfish-qtcreator,amyvmiwei/qt-creator,kuba1/qtcreator,farseerri/git_code,Distrotech/qtcreator,Distrotech/qtcreator,hdweiss/qt-creator-visualizer,azat/qtcreator,omniacreator/qtcreator,duythanhphan/qt-creator,darksylinc/qt-creator,bakaiadam/collaborative_qt_creator,farseerri/git_code,maui-packages/qt-creator,duythanhphan/qt-creator,jonnor/qt-creator,darksylinc/qt-creator,martyone/sailfish-qtcreator,amyvmiwei/qt-creator,ostash/qt-creator-i18n-uk,sandsmark/qtcreator-minimap,omniacreator/qtcreator,martyone/sailfish-qtcreator,dmik/qt-creator-os2,colede/qtcreator,AltarBeastiful/qt-creator,pcacjr/qt-creator,syntheticpp/qt-creator,yinyunqiao/qtcreator,jonnor/qt-creator,KDAB/KDAB-Creator,pcacjr/qt-creator,Distrotech/qtcreator,colede/qtcreator,darksylinc/qt-creator,martyone/sailfish-qtcreator,richardmg/qtcreator,KDAB/KDAB-Creator,omniacreator/qtcreator,bakaiadam/collaborative_qt_creator,KDAB/KDAB-Creator,omniacreator/qtcreator,maui-packages/qt-creator,martyone/sailfish-qtcreator,xianian/qt-creator,kuba1/qtcreator,danimo/qt-creator,kuba1/qtcreator,renatofilho/QtCreator,hdweiss/qt-creator-visualizer,richardmg/qtcreator,omniacreator/qtcreator,Distrotech/qtcreator,kuba1/qtcreator,Distrotech/qtcreator,kuba1/qtcreator,pcacjr/qt-creator,danimo/qt-creator,amyvmiwei/qt-creator,ostash/qt-creator-i18n-uk,yinyunqiao/qtcreator,pcacjr/qt-creator,bakaiadam/collaborative_qt_creator,colede/qtcreator,pcacjr/qt-creator,syntheticpp/qt-creator,malikcjm/qtcreator,duythanhphan/qt-creator,azat/qtcreator,sandsmark/qtcreator-minimap,kuba1/qtcreator,sandsmark/qtcreator-minimap,syntheticpp/qt-creator,danimo/qt-creator,azat/qtcreator,darksylinc/qt-creator,farseerri/git_code,duythanhphan/qt-creator,jonnor/qt-creator,AltarBeastiful/qt-creator,KDE/android-qt-creator,maui-packages/qt-creator,richardmg/qtcreator,renatofilho/QtCreator,kuba1/qtcreator,azat/qtcreator,hdweiss/qt-creator-visualizer,dmik/qt-creator-os2,KDAB/KDAB-Creator,ostash/qt-creator-i18n-uk,danimo/qt-creator,renatofilho/QtCreator,danimo/qt-creator,martyone/sailfish-qtcreator,azat/qtcreator,ostash/qt-creator-i18n-uk,Distrotech/qtcreator,xianian/qt-creator,maui-packages/qt-creator,jonnor/qt-creator,amyvmiwei/qt-creator,syntheticpp/qt-creator,duythanhphan/qt-creator,yinyunqiao/qtcreator,pcacjr/qt-creator,hdweiss/qt-creator-visualizer,colede/qtcreator,syntheticpp/qt-creator,bakaiadam/collaborative_qt_creator,yinyunqiao/qtcreator,AltarBeastiful/qt-creator,KDE/android-qt-creator,dmik/qt-creator-os2,ostash/qt-creator-i18n-uk,yinyunqiao/qtcreator,maui-packages/qt-creator,KDE/android-qt-creator,KDE/android-qt-creator,hdweiss/qt-creator-visualizer,duythanhphan/qt-creator,dmik/qt-creator-os2,malikcjm/qtcreator,KDE/android-qt-creator,yinyunqiao/qtcreator,KDAB/KDAB-Creator,xianian/qt-creator,xianian/qt-creator,AltarBeastiful/qt-creator,pcacjr/qt-creator,martyone/sailfish-qtcreator,KDE/android-qt-creator,sandsmark/qtcreator-minimap,amyvmiwei/qt-creator,darksylinc/qt-creator,richardmg/qtcreator,darksylinc/qt-creator,jonnor/qt-creator,syntheticpp/qt-creator,KDAB/KDAB-Creator,AltarBeastiful/qt-creator,martyone/sailfish-qtcreator,AltarBeastiful/qt-creator,malikcjm/qtcreator,AltarBeastiful/qt-creator,yinyunqiao/qtcreator,bakaiadam/collaborative_qt_creator,dmik/qt-creator-os2,maui-packages/qt-creator,syntheticpp/qt-creator,azat/qtcreator,danimo/qt-creator,duythanhphan/qt-creator,richardmg/qtcreator,colede/qtcreator,farseerri/git_code,darksylinc/qt-creator,farseerri/git_code,renatofilho/QtCreator,kuba1/qtcreator,bakaiadam/collaborative_qt_creator,xianian/qt-creator,AltarBeastiful/qt-creator,danimo/qt-creator,hdweiss/qt-creator-visualizer,maui-packages/qt-creator