Memory leak in QtDesigner: widgetdatabase.cpp, scaleFormTemplate

The domUI object is deleted at the end of the function. If the call to elementWidget fails, then the function returns prematurely without deleting the domUI object.

Should delete explicitly, or use QScopedPointer.

This is reported by coverity at https://scan3.coverity.com/reports.htm#v42553/p10113/fileInstanceId=33001381&defectInstanceId=9019821&mergedDefectId=21962