v0.6.2: more safety checks in tengu logic

core/src/main/java/com/shatteredpixel/shatteredpixeldungeon/actors/mobs/Tengu.java

@@ -181,6 +181,7 @@ public class Tengu extends Mob {
 		}
 
 		if (enemy == null) enemy = chooseEnemy();
+		if (enemy == null) return;
 
 		int newPos;
 		//if we're in phase 1, want to warp around within the room