fix

src/components/Widgets/Classroom/UserClassroomCard/UserClassroomCard.vue

@@ -2,7 +2,7 @@
   <q-card-section class="classroom-card row">
     <div class="right-side col-6">
       <img class="thumbnail"
-           :src="registration.classroom_info.thumbnail">
+           :src="registration.classroom_info.thumbnail ? registration.classroom_info.thumbnail: '/img/sample-post-thumbnail.jpg'">
       <q-btn color="primary"
              :to="{name: showPageRouteName, params: {id: registration.classroom_info.id}}">
         مشاهده