fix fetch

@@ -297,10 +297,11 @@ export default {
     async onFetch() {
       const topicId = parseInt(this.topicId, 10);
 
-      if (!topicId) {
-        return;
+      if (!topicId || this.fetching) {
+        return [];
       }
 
+      this.fetching = true;
       this.page = this.page || 1;
 
       let result = get(this.listPreCache, `${this.topicId}-${this.page}`);
@@ -312,6 +313,7 @@ export default {
         });
       }
 
+      this.fetching = false;
       let list = [];
 
       if (result.code === 200) {