LibWeb: Reset MessagePort's worker event target when it is disentangled

Author: https://github.com/trflynn89
Commit: d44dd756b3
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/1835
Reviewed-by: https://github.com/ADKaster ✅

Userland/Libraries/LibWeb/HTML/MessagePort.cpp

@@ -128,6 +128,8 @@ void MessagePort::disentangle()
     m_remote_port = nullptr;
 
     m_socket = nullptr;
+
+    m_worker_event_target = nullptr;
 }
 
 // https://html.spec.whatwg.org/multipage/web-messaging.html#entangle