diff --git a/src/App.vue b/src/App.vue
index d7261b6..7b2a795 100644
--- a/src/App.vue
+++ b/src/App.vue
@@ -97,7 +97,7 @@ export default {
       try {
         const data = JSON.parse(event.data, (key, value, ctx) => {
           if (typeof value === 'number' && value > Number.MAX_SAFE_INTEGER) {
-            return ctx.source;
+            return ctx?.source || '';
           }
           return value;
         })