Fixes to immobilization, wyverns, bug fixes

Author: lare96

data/game/def/npcs/npc_combat.json

@@ -13,6 +13,8 @@
 import java.util.Queue;
 import java.util.Set;
 
+import static com.google.common.base.Preconditions.checkState;
+
 /**
  * Per-mob action scheduler responsible for registering and processing {@link Action}s each game cycle.
  * <p>
@@ -110,7 +112,9 @@ public void submit(Action<?> action) {
      * @param action The action to submit if its concrete type is not already active.
      * @return {@code true} if the action was not already active, and therefore submitted.
      */
+    @Deprecated // todo remove, actions should monitor their own lifecycle
     public boolean submitIfAbsent(Action<?> action) {
+        checkState(!action.getClass().isAnonymousClass(), "Anonymous classes cannot be used with submitIfAbsent.");
         String type = action.getClass().getName();
         if (!types.contains(type)) {
             submit(action);