Three issues: - When saving a file, without extension added, and no filename provided, the saving code received the directory name only. That's a potential danger of getting directories deleted. Added in the saveover() function a check for this, and return an error when you try to save over a directory. - Screendump did not add file extensions yet, when indicated todo so. - Screendump code was duplicating all image type cases, whilst we have a nice BKE_write_ibuf() call for that now. (Bug was that this code did not check for BMP, saving the file in default format.)