[WebIDL] Hoist protectedThis reference in JSEventListener::handleEvent()

https://bugs.webkit.org/show_bug.cgi?id=248328

Reviewed by Yusuke Suzuki.

While this change is non-observable since the only caller of handleEvent(),
innerInvokeEventListeners(), keeps it as RefPtr, theoretically both getCallData() and
jsFunction->get() may remove currently running event listener and cause its destruction.

* Source/WebCore/bindings/js/JSEventListener.cpp:
(WebCore::JSEventListener::handleEvent):

Canonical link: https://commits.webkit.org/257027@main

Source/WebCore/bindings/js/JSEventListener.cpp

@@ -180,6 +180,8 @@ void JSEventListener::handleEvent(ScriptExecutionContext& scriptExecutionContext
 
     JSValue handleEventFunction = jsFunction;
 
+    Ref protectedThis { *this };
+
     auto callData = JSC::getCallData(handleEventFunction);
 
     // If jsFunction is not actually a function and this is an EventListener, see if it implements callback interface.
@@ -203,8 +205,6 @@ void JSEventListener::handleEvent(ScriptExecutionContext& scriptExecutionContext
         }
     }
 
-    Ref<JSEventListener> protectedThis(*this);
-
     MarkedArgumentBuffer args;
     args.append(toJS(lexicalGlobalObject, globalObject, &event));
     ASSERT(!args.hasOverflowed());