add empty check for ActionApplier & RequirementApplier

Author: HSGamer

src/main/java/me/hsgamer/bettergui/action/ActionApplier.java

@@ -40,6 +40,15 @@ public ActionApplier(Menu menu, Object value) {
     this(ActionBuilder.INSTANCE.build(menu, value));
   }
 
+  /**
+   * Check if the applier is empty
+   *
+   * @return true if it is empty
+   */
+  public boolean isEmpty() {
+    return actions.isEmpty();
+  }
+
   /**
    * Apply the action to the process without the next action
    *

src/main/java/me/hsgamer/bettergui/requirement/RequirementApplier.java

@@ -108,6 +108,15 @@ public static Map<BukkitClickType, RequirementApplier> convertClickRequirementAp
     return clickRequirements;
   }
 
+  /**
+   * Check if the applier is empty
+   *
+   * @return true if it is empty
+   */
+  public boolean isEmpty() {
+    return requirementSets.isEmpty() && failActionApplier.isEmpty();
+  }
+
   /**
    * Get the result of the requirement
    *