fix(formController): remove scope reference when form is destroyed

Closes #9315

Author: shahata

src/ng/directive/form.js

@@ -495,15 +495,13 @@ var formDirectiveFactory = function(isNgForm) {
                 parentFormCtrl.$$renameControl(controller, alias);
               });
             }
-            if (parentFormCtrl !== nullFormCtrl) {
-              formElement.on('$destroy', function() {
-                parentFormCtrl.$removeControl(controller);
-                if (alias) {
-                  setter(scope, alias, undefined, alias);
-                }
-                extend(controller, nullFormCtrl); //stop propagating child destruction handlers upwards
-              });
-            }
+            formElement.on('$destroy', function() {
+              parentFormCtrl.$removeControl(controller);
+              if (alias) {
+                setter(scope, alias, undefined, alias);
+              }
+              extend(controller, nullFormCtrl); //stop propagating child destruction handlers upwards
+            });
           }
         };
       }

test/ng/directive/formSpec.js

@@ -58,6 +58,26 @@ describe('form', function() {
     expect(form.alias).toBeUndefined();
   });
 
+  it('should remove scope reference when form with no parent form is removed from the DOM', function() {
+    var formController;
+    scope.ctrl = {};
+    doc = $compile(
+      '<div><form name="ctrl.myForm" ng-if="formPresent">' +
+        '<input name="alias" ng-model="value" />' +
+      '</form></div>')(scope);
+
+    scope.$digest();
+    expect(scope.ctrl.myForm).toBeUndefined();
+
+    scope.$apply('formPresent = true');
+    expect(scope.ctrl.myForm).toBeDefined();
+
+    formController = doc.find('form').controller('form');
+    expect(scope.ctrl.myForm).toBe(formController);
+
+    scope.$apply('formPresent = false');
+    expect(scope.ctrl.myForm).toBeUndefined();
+  });
 
   it('should use ngForm value as form name', function() {
     doc = $compile(