Fix a warning when setActiveFocusOnTab(false) for root item

Task-number: QTBUG-31114

Change-Id: I4d6aac534fbc1e84593e4d7084e6a892eea4256c
Reviewed-by: Caroline Chao <caroline.chao@digia.com>
Reviewed-by: Jens Bache-Wiig <jens.bache-wiig@digia.com>
Respond appropriately to textFormat changed

If the text has not changed when textFormat changes between states other
than RichText, the text was not re-laid-out. This is necessary if the
text includes control tags.

Task-number: QTBUG-31191
Change-Id: I3c6f5343aa85e8337b90cf86748a696d5742e906
Reviewed-by: Andrew den Exter <andrew.den.exter@qinetic.com.au>
Prefer qFatal to assert for failure condition

Otherwise the explanatory message won't be seen in release mode.

Change-Id: I5c9fbc86753ac5ecea3d0714b8f17207f6b713d6
Reviewed-by: Alan Alpert <aalpert@blackberry.com>