events: add null check for the signal of EventTarget

This will improve the Web compatibility.
Passing null as the signal should throw an error.
WPT says "Passing null as the signal should throw".
Please see https://github.com/web-platform-tests/wpt/blob/master/dom/events/AddEventListenerOptions-signal.any.js

lib/internal/event_target.js

@@ -482,6 +482,10 @@ class EventTarget {
     }
     type = String(type);
 
+    if (signal === null) {
+      throw new ERR_INVALID_ARG_TYPE('options.signal', 'AbortSignal', signal);
+    }
+
     if (signal) {
       if (signal.aborted) {
         return;

test/parallel/test-eventtarget-whatwg-signal.js

@@ -4,6 +4,7 @@ require('../common');
 
 const {
   strictEqual,
+  throws
 } = require('assert');
 
 // Manually ported from: wpt@dom/events/AddEventListenerOptions-signal.any.js
@@ -157,3 +158,7 @@ const {
   }, { once: true });
   et.dispatchEvent(new Event('foo'));
 }
+{
+  const et = new EventTarget();
+  throws(() => et.addEventListener('foo', () => {}, {signal: null}));
+}