fix hiding header for non group (#2512)

ng2-components/ng2-activiti-form/src/components/widgets/container/container.widget.scss

@@ -4,6 +4,10 @@
     $accent: map-get($theme, accent);
     $warn: map-get($theme, warn);
 
+    .hidden{
+        display: none;
+    }
+
     .adf {
         &-field-list {
             padding: 0;

ng2-components/ng2-activiti-tasklist/src/components/start-task.component.ts

@@ -90,7 +90,9 @@ export class StartTaskComponent implements OnInit {
 
     public start(): void {
         if (this.startTaskmodel.name) {
-            this.startTaskmodel.category = this.appId.toString();
+            if(this.appId) {
+                this.startTaskmodel.category = this.appId.toString();
+            }
             this.taskService.createNewTask(new TaskDetailsModel(this.startTaskmodel))
                 .switchMap((createRes: any) =>
                     this.attachForm(createRes.id, this.formKey).defaultIfEmpty(createRes)