fix null prt release crash

com.unity.uiwidgets/Runtime/engine/UIWidgetsPanelWrapper.cs

             }
         }
         public void Destroy() {
-            UIWidgetsPanel_onDisable(ptr: _ptr);
-            UIWidgetsPanel_dispose(ptr: _ptr);
-            _ptr = IntPtr.Zero;
+            if (_ptr != IntPtr.Zero) {
+                UIWidgetsPanel_onDisable(ptr: _ptr);
+                UIWidgetsPanel_dispose(ptr: _ptr);
+                _ptr = IntPtr.Zero;
+            }
+
             _handle.Free();
             _handle = default;