Fix memory leak when closing images opened from thumbnail mode

src/slideshow.c

@@ -686,6 +686,7 @@ void feh_filelist_image_remove(winwidget winwid, char do_delete)
 			filelist = feh_file_rm_and_free(filelist, winwid->file);
 		else
 			filelist = feh_file_remove_from_list(filelist, winwid->file);
+		winwid->file = NULL;
 		winwidget_destroy(winwid);
 	}
 }

src/winwidget.c

@@ -755,6 +755,8 @@ void winwidget_destroy(winwidget winwid)
 		free(winwid->name);
 	if (winwid->gc)
 		XFreeGC(disp, winwid->gc);
+	if ((winwid->type == WIN_TYPE_THUMBNAIL_VIEWER) && (winwid->file != NULL))
+		gib_list_free(winwid->file);
 	if (winwid->im)
 		gib_imlib_free_image_and_decache(winwid->im);
 	free(winwid);