fix(ngHref): allow setting href to empty string

src/ng/directive/booleanAttrs.js

@@ -380,7 +380,7 @@ forEach(['src', 'srcset', 'href'], function(attrName) {
         }
 
         attr.$observe(normalized, function(value) {
-          if (!value)
+          if (!value && attrName === 'src')
              return;
 
           attr.$set(name, value);

test/ng/directive/booleanAttrsSpec.js

@@ -246,6 +246,18 @@ describe('ngHref', function() {
   }));
 
 
+  it('should remote href value when interpolated value is empty', inject(function($compile, $rootScope) {
+    element = $compile('<div ng-href="{{id}}"></div>')($rootScope);
+    $rootScope.$digest();
+    expect(element.attr('href')).toEqual('');
+
+    $rootScope.$apply(function() {
+      $rootScope.id = 1;
+    });
+    expect(element.attr('href')).toEqual('1');
+  }));
+
+
   it('should bind href even if no interpolation', inject(function($rootScope, $compile) {
     element = $compile('<a ng-href="http://server"></a>')($rootScope)
     $rootScope.$digest();