HelpManager: Use QTC_ASSERT
HelpManager: Use QTC_ASSERT

We have many conditions where we return empty default values when the
help engine is not yet set up. These deserve a warning.

Change-Id: Ib7235d344f93ab7a6e2e0ee126c3593818b8a8b0
Reviewed-by: Eike Ziller <c142da16c73a95a82d35191bcc55b22835617128@theqtcompany.com>

kuba1/qtcreator,AltarBeastiful/qt-creator,amyvmiwei/qt-creator,kuba1/qtcreator,Distrotech/qtcreator,Distrotech/qtcreator,farseerri/git_code,Distrotech/qtcreator,amyvmiwei/qt-creator,AltarBeastiful/qt-creator,martyone/sailfish-qtcreator,kuba1/qtcreator,amyvmiwei/qt-creator,martyone/sailfish-qtcreator,xianian/qt-creator,martyone/sailfish-qtcreator,kuba1/qtcreator,farseerri/git_code,kuba1/qtcreator,xianian/qt-creator,xianian/qt-creator,xianian/qt-creator,AltarBeastiful/qt-creator,kuba1/qtcreator,xianian/qt-creator,danimo/qt-creator,kuba1/qtcreator,xianian/qt-creator,danimo/qt-creator,martyone/sailfish-qtcreator,danimo/qt-creator,martyone/sailfish-qtcreator,AltarBeastiful/qt-creator,kuba1/qtcreator,xianian/qt-creator,AltarBeastiful/qt-creator,amyvmiwei/qt-creator,danimo/qt-creator,amyvmiwei/qt-creator,farseerri/git_code,farseerri/git_code,xianian/qt-creator,danimo/qt-creator,Distrotech/qtcreator,danimo/qt-creator,kuba1/qtcreator,martyone/sailfish-qtcreator,danimo/qt-creator,farseerri/git_code,amyvmiwei/qt-creator,AltarBeastiful/qt-creator,farseerri/git_code,amyvmiwei/qt-creator,danimo/qt-creator,AltarBeastiful/qt-creator,AltarBeastiful/qt-creator,martyone/sailfish-qtcreator,farseerri/git_code,farseerri/git_code,Distrotech/qtcreator,martyone/sailfish-qtcreator,martyone/sailfish-qtcreator,Distrotech/qtcreator,xianian/qt-creator,amyvmiwei/qt-creator,Distrotech/qtcreator,danimo/qt-creator