Avoid crashes on MS-Windows when JPEG images are too large.

Avoid crashes on MS-Windows when JPEG images are too large.

 src/image.c (x_create_x_image_and_pixmap) [HAVE_NTGUI]: If
 CreateDIBSection returns an error indication, zero out *ximg after
 destroying the image.  This avoids crashes in memory allocations
 due to the fact that some of the callers also call
 x_destroy_x_image, which will attempt to free an already free'd
 block of memory.