Don't report an error when loading a saved game from the command

line unless there really _is_ an error!

[originally from svn r6203]

gtk.c

@@ -1447,6 +1447,7 @@ static frontend *new_window(char *arg, char **error)
 			" nor a save file (%.400s)", err, strerror(errno));
 	    } else {
 		err = midend_deserialise(fe->me, savefile_read, fp);
+                if (err)
                     sprintf(errbuf, "%.800s", err);
                 fclose(fp);
 	    }