Issue #5232 - PSD export issue

In psd-save.c, fix erroneous call to gimp_item_get_image(), which
was being called with an image-id, instead of a drawable-id,
potentially causing an error or wrong results if the image-id did
not correspond to an existing item, or if the corresponding item
did not belong to the exported image.

plug-ins/file-psd/psd-save.c

@@ -1829,7 +1829,7 @@ get_pixel_format (gint32 drawableID)
       g_return_val_if_reached (NULL);
     }
 
-  bpc = get_bpc (gimp_item_get_image (image_id));
+  bpc = get_bpc (image_id);
 
   sprintf (format, "%s u%d", model, 8 * bpc);