image: Add NULL checks for return value of _pixman_image_for_color()

This fixes crash in pixman_image_composite32().

Originally fixed by Yoshitaro Makise.

Reviewed-by: Bryce Harrington <b.harrington@samsung.com>
Signed-off-by: Bryce Harrington <b.harrington@samsung.com>
Revert "[ft] Fix memory bug in copying bitmaps"

This reverts commit a0f556f37fb7016aa304b7cf0e811c0d38f0b969.

The change was clearly wrong now that I read.  I was probably
tricked by what was fixed in the follow-up commit
e738079302a968b7b1fb9101cd4d92a8887bedce.