Fix a potential crash due to the fact that _q_UpdateIndex() is reentered
Fix a potential crash due to the fact that _q_UpdateIndex() is reentered

This is confirmed to resolve a number of problems from the original
reportee.  It's already fixed in Qt 4.6 in a more wider fix, but this
one liner is a good to have in Qt 4.5.x anyway.

Task-number: 258194
Reviewed-by: alexis

igor-sfdc/qt-wk,pruiz/wkhtmltopdf-qt,radekp/qt,radekp/qt,igor-sfdc/qt-wk,igor-sfdc/qt-wk,igor-sfdc/qt-wk,igor-sfdc/qt-wk,igor-sfdc/qt-wk,pruiz/wkhtmltopdf-qt,igor-sfdc/qt-wk,igor-sfdc/qt-wk,radekp/qt,pruiz/wkhtmltopdf-qt,pruiz/wkhtmltopdf-qt,pruiz/wkhtmltopdf-qt,pruiz/wkhtmltopdf-qt,radekp/qt,RLovelett/qt,RLovelett/qt,RLovelett/qt,radekp/qt,KDE/qt,igor-sfdc/qt-wk,pruiz/wkhtmltopdf-qt,pruiz/wkhtmltopdf-qt,KDE/qt,radekp/qt,RLovelett/qt,igor-sfdc/qt-wk,KDE/qt,KDE/qt,KDE/qt,pruiz/wkhtmltopdf-qt,RLovelett/qt,KDE/qt,radekp/qt,RLovelett/qt,igor-sfdc/qt-wk,radekp/qt,pruiz/wkhtmltopdf-qt,radekp/qt,KDE/qt,RLovelett/qt,RLovelett/qt,RLovelett/qt,pruiz/wkhtmltopdf-qt,RLovelett/qt,RLovelett/qt,radekp/qt,KDE/qt