fix($animate): reset classNameFilter to null when a disallowed RegExp is used

Closes #14913

Author: gkalpak

src/ng/animate.js

@@ -252,6 +252,7 @@ var $AnimateProvider = ['$provide', /** @this */ function($provide) {
       if (classNameFilter) {
         var reservedRegex = new RegExp('[(\\s|\\/)]' + NG_ANIMATE_CLASSNAME + '[(\\s|\\/)]');
         if (reservedRegex.test(classNameFilter.toString())) {
+          classNameFilter = null;
           throw $animateMinErr('nongcls', '$animateProvider.classNameFilter(regex) prohibits accepting a regex value which matches/contains the "{0}" CSS class.', NG_ANIMATE_CLASSNAME);
         }
       }

test/ngAnimate/animateSpec.js

@@ -277,6 +277,20 @@ describe('animations', function() {
       })
     );
 
+    it('should clear the `classNameFilter` if a disallowed RegExp is passed',
+      module(function($animateProvider) {
+        var validRegex = /no-ng-animate/;
+        var invalidRegex = /no ng-animate/;
+
+        $animateProvider.classNameFilter(validRegex);
+        expect($animateProvider.classNameFilter()).toEqual(validRegex);
+
+        // eslint-disable-next-line no-empty
+        try { $animateProvider.classNameFilter(invalidRegex); } catch (err) {}
+        expect($animateProvider.classNameFilter()).toBeNull();
+      })
+    );
+
     it('should complete the leave DOM operation in case the classNameFilter fails', function() {
       module(function($animateProvider) {
         $animateProvider.classNameFilter(/memorable-animation/);