events: reset the event target to null

Allow an event to be dispatched multiple times by resetting the event
target to `null` when dispatch is complete.

lib/internal/event_target.js

@@ -464,7 +464,7 @@ class EventTarget {
     }
 
     if (event !== undefined)
-      event[kTarget] = undefined;
+      event[kTarget] = null;
   }
 
   [kCreateEvent](nodeValue, type) {

test/parallel/test-eventtarget.js

@@ -162,6 +162,27 @@ let asyncTest = Promise.resolve();
   eventTarget.dispatchEvent(ev);
 }
 
+{
+  // Same event dispatched multiple times.
+  const event = new Event('foo');
+  const eventTarget1 = new EventTarget();
+  const eventTarget2 = new EventTarget();
+
+  eventTarget1.addEventListener('foo', common.mustCall((event) => {
+    strictEqual(event.target, eventTarget1);
+  }));
+
+  eventTarget2.addEventListener('foo', common.mustCall((event) => {
+    strictEqual(event.target, eventTarget2);
+  }));
+
+  eventTarget1.dispatchEvent(event);
+  strictEqual(event.target, null);
+
+  eventTarget2.dispatchEvent(event);
+  strictEqual(event.target, null);
+}
+
 {
   const eventTarget = new EventTarget();
   const event = new Event('foo', { cancelable: true });