Add a formula to check there is no deadlock

ds/trains0.xml

@@ -302,6 +302,10 @@ some other trains are waiting on B.</label>
 			</comment>
 		</query>
 		<query>
+			<formula>A[] not deadlock</formula>
+			<comment></comment>
+		</query>
+		<query>
 			<formula>E&lt;&gt; TrainBA(1).BA &amp; TrainBA(2).BA
 			</formula>
 			<comment>