Created attachment 4999 
fixes inconsistent dnd behaviour

When dragging a file from an external app (i.e. xfdesktop), the default action varies between "move" and "copy" depending on whether the dragged file is shown in a thunar window or not.

This behaviour is caused by using thunar_file_cache_lookup() in thunar_file_accepts_drop() and defaulting to "copy" if the source file is not in the cache (which is the case if it's not shown in any thunar window). The attached patch fixes this by using thunar_file_get() instead.