fix(utils): should have no effect when called addEventListener/remove…

…EventListener without eventListener.

lib/utils.js

@@ -96,6 +96,9 @@ function patchEventTargetMethods(obj) {
   // This is required for the addEventListener hook on the root zone.
   obj[keys.common.addEventListener] = obj.addEventListener;
   obj.addEventListener = function (eventName, handler, useCapturing) {
+    if (!handler) {
+      return;
+    }
     var eventType = eventName + (useCapturing ? '$capturing' : '$bubbling');
     var fn;
     //Ignore special listeners of IE11 & Edge dev tools, see https://github.com/angular/zone.js/issues/150
@@ -129,6 +132,9 @@ function patchEventTargetMethods(obj) {
   // This is required for the removeEventListener hook on the root zone.
   obj[keys.common.removeEventListener] = obj.removeEventListener;
   obj.removeEventListener = function (eventName, handler, useCapturing) {
+    if (!handler) {
+      return;
+    }
     var eventType = eventName + (useCapturing ? '$capturing' : '$bubbling');
     if (handler[boundFnsKey] && handler[boundFnsKey][eventType]) {
       var _bound = handler[boundFnsKey];

test/patch/element.spec.js

@@ -113,6 +113,20 @@ describe('element', function () {
     expect(eventListener.handleEvent).not.toHaveBeenCalled();
   });
 
+  it('should have no effect while calling addEventListener without listener', function () {
+    expect(function() {
+      button.addEventListener('click', null);
+      button.addEventListener('click', undefined);
+    }).not.toThrowError();
+  });
+
+  it('should have no effect while calling removeEventListener without listener', function () {
+    expect(function() {
+      button.removeEventListener('click', null);
+      button.removeEventListener('click', undefined);
+    }).not.toThrowError();
+  });
+
 
   it('should only add a listener once for a given set of arguments', function() {
     var log = [];