MOBILE-1701 assign: Fix error when leaving edit view too soon

Author: dpalou

www/addons/mod/assign/controllers/edit.js

@@ -137,7 +137,7 @@ angular.module('mm.addons.mod_assign')
     // Function called when user wants to leave view without saving.
     function leaveView() {
         // Check that we're leaving the current view, since the user can navigate to other views from here.
-        if ($ionicHistory.currentView() !== currentView) {
+        if ($ionicHistory.currentView() !== currentView || !$scope.userSubmission) {
             // It's another view.
             originalBackFunction();
             return;