Properly parse "characters" formed by two QChars

This fixes the crash at 287138, it does still not really fix the flaw in the algorithm in TextPagePrivate::breakWordIntoCharacters
when there are two strings with the same text and the same bounding rectangle in the same page, but i still don't know how to fix that problem properly,
so i've fixed a bug that was generating the situation for files that actually do not have it
BUGS: 287138