作答，多项填空题，必答且答案为空校验；

src/views/Answer/questions/QInputBlanks.vue

@@ -122,6 +122,9 @@ export default defineComponent({
           error = "";
         }
       }
+      if (Object.keys(answer || {}).every((key) => !answer[key])) {
+        answer = null
+      }
       context.emit("update:error", error);
       context.emit("update:answer", answer);
     }