Fix possible NPE in RegionState

spring-statemachine-core/src/main/java/org/springframework/statemachine/state/RegionState.java

@@ -110,7 +110,9 @@ public class RegionState<S, E> extends AbstractState<S, E> {
 	@Override
 	public void exit(StateContext<S, E> context) {
 		for (Region<S, E> region : getRegions()) {
-			region.getState().exit(context);
+			if (region.getState() != null) {
+				region.getState().exit(context);
+			}
 			region.stop();
 		}
 		Collection<? extends Action<S, E>> actions = getExitActions();

spring-statemachine-core/src/test/java/org/springframework/statemachine/state/EndStateTests.java

@@ -80,8 +80,7 @@ public class EndStateTests extends AbstractStateMachineTests {
 		assertThat(machine.getState().getIds(), contains(TestStates3.READY));
 	}
 
-	// disable for now, fix in other ticket
-	//@Test
+	@Test
 	public void testEndStatesWithRegionsDefinedInStates() throws InterruptedException {
 		context.register(Config3.class);
 		context.refresh();