This amends commit 8f4a537, which aimed to correct NULL dereference because of
missing check of gdImageCreateTrueColor() / gdImageCreate() return value. That
commit checks for negative crop rectangle width and height, but
gdImageCreate*() can also return NULL when width * height overflows. Hence
NULL deref is still possible, as gdImageSaveAlpha() and gdImagePaletteCopy()
is called before dst == NULL check.
This moves NULL check to happen right after gdImageCreate*(). It also removes
width and height check before gdImageCreate*(), as the same check is done by
image create functions (with an extra warning).
From thoger redhat com
Initial fix was PHP stuff
This one is libgd fix.
- filter invalid crop size
- dont try to copy on invalid position
- fix crop size when out of src image
- fix possible NULL deref
- fix possible integer overfloow
