This continues 68762151db
When doing format conversion, the optimized inplace codepath did not
check if the image data was external, i.e. if the QImage had been
created by the constructor taking an existing external buffer.
The previous commit fixed the readonly case. But in the case of the
QImage constructor taking non-const uchar*, data will be read-write,
but still external. This would of course crash if the converter tries
to realloc it.
Task-number: QTBUG-44610
Change-Id: I94d275d464e8af221682b538fc3e4897a59c061e
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@theqtcompany.com>