fix(directive): handle interpolation of undefined keys correctly in u…

…pdateTranslations, fixes issues in #971

src/directive/translate.js

@@ -218,7 +218,8 @@ angular.module('pascalprecht.translate')
         // Master update function
         var updateTranslations = function () {
           for (var key in translationIds) {
-            if (translationIds.hasOwnProperty(key)) {
+
+            if (translationIds.hasOwnProperty(key) && translationIds[key] !== undefined) {
               updateTranslation(key, translationIds[key], scope, scope.interpolateParams, scope.defaultText);
             }
           }

test/unit/directive/translate.spec.js

@@ -142,6 +142,13 @@ describe('pascalprecht.translate', function () {
         expect(element.text()).toBe('TEXT');
       });
 
+      it('should return empty translation if translationId scope Variable does not exist and if its passed as interpolation', function () {
+        element = $compile('<div translate>{{translationIdNotExisting}}</div>')($rootScope);
+        $rootScope.$digest();
+        expect(element.text()).toBe('');
+      });
+
+
       it('should return translation prepended by additional content when passed as interpolation', function () {
         $rootScope.translationId = 'TRANSLATION_ID';
         element = $compile('<div translate>abc{{translationId}}')($rootScope);

test/unit/filter/translate.spec.js

@@ -39,7 +39,9 @@ describe('pascalprecht.translate', function () {
     it('should return with translation id if translation doesn\'t exist', function () {
       expect($translate('WOOP')).toEqual('WOOP');
     });
-
+    it('should return with translation id if translation doesn\'t exist', function () {
+         expect($translate(null)).toEqual(null);
+    });
     it('should return translation if translation id exist', function () {
       expect($translate('TRANSLATION_ID')).toEqual('Lorem Ipsum ');
     });