added fallback option to enemy movement when out of space

src/enemy.cc

@@ -34,7 +34,9 @@ long_result enemy_base::act(level *lvl, character *pc, bool hostile) {
                                 target = tmp;
                 }
 
-                pos = target;
+                if (target.x != BIG_NUMBER)
+                        pos = target;
+
                 return {NOTHING, ""};
         }