[ADF-1456] timeAgo Pipe - Return invalid date when the input is empty. (#2240)

* [ADF-1456]  timeAgo Pipe - Return invalid date when the input is empty.

* Return the empty string instead of an Invalid Date error when  the given date is empty.
* Added test cases.

* [ADF-1456] timeAgo Pipe - Return invalid date when the input is empty.

* Changed test case to handle modified  time zone.

ng2-components/ng2-alfresco-core/src/pipes/time-ago.pipe.spec.ts

@@ -0,0 +1,42 @@
+/*!
+ * @license
+ * Copyright 2016 Alfresco Software, Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { TimeAgoPipe } from './time-ago.pipe';
+
+describe('TimeAgoPipe', () => {
+
+    let pipe: TimeAgoPipe;
+
+    beforeEach(() => {
+        pipe = new TimeAgoPipe();
+    });
+
+    it('should return time difference for a given date', () => {
+        let date = new Date();
+        expect(pipe.transform(date)).toBe('a few seconds ago');
+    });
+
+    it('should return exact date if given date is more than seven days ', () => {
+        let date = new Date('1990-11-03T15:25:42.749');
+        expect(pipe.transform(date)).toBe('03/11/1990 15:25');
+    });
+
+    it('should return empty string if given date is empty', () => {
+        expect(pipe.transform(null)).toBe('');
+        expect(pipe.transform(undefined)).toBe('');
+    });
+});

ng2-components/ng2-alfresco-core/src/pipes/time-ago.pipe.ts

@@ -25,8 +25,11 @@ import { Pipe, PipeTransform } from '@angular/core';
 export class TimeAgoPipe implements PipeTransform {
 
     transform(value: Date) {
-        const then = moment(value);
-        const diff = moment().diff(then, 'days');
-        return diff > 7 ? then.format('DD/MM/YYYY HH:mm') : then.fromNow();
+        if (value !== null && value !== undefined ) {
+            const then = moment(value);
+            const diff = moment().diff(then, 'days');
+            return diff > 7 ? then.format('DD/MM/YYYY HH:mm') : then.fromNow();
+        }
+        return '';
     }
 }