add another check when deleting an image

src/views/GiftedDetails.vue

@@ -202,6 +202,9 @@ export default class GiftedDetails extends Vue {
   }
 
   async deleteImage() {
+    if (!this.imageUrl) {
+      return;
+    }
     try {
       const identity = await libsUtil.getIdentity(this.activeDid);
       const token = await accessToken(identity);