Bugfix for python Image.save()

[ #6702 ] Image doesn't get saved after painting & packing
IMB_saveiff - (general saving function), does not write a file when the image is packed.
so write a file with writePackedFile for packed files.

source/blender/blenkernel/intern/packedFile.c

@@ -286,7 +286,7 @@ int writePackedFile(char * filename, PackedFile *pf, int guimode)
 	char tempname[FILE_MAXDIR + FILE_MAXFILE];
 /*  	void * data; */
 	
-	waitcursor(1);
+	if (guimode) waitcursor(1);
 	
 	strcpy(name, filename);
 	BLI_convertstringcode(name, G.sce, G.scene->r.cfra);