feat:保存

src/services/common.ts

@@ -159,6 +159,10 @@ export const save = async (
    meta2d.store.data.component = true
   }
   const data: Meta2dBackData = meta2d.data();
+  if(!data.pens.length){
+    MessagePlugin.warning('画布为空，无法保存！');
+    return;
+  }
   if (!(user && user.id)) {
     MessagePlugin.warning(noLoginTip);
     localforage.setItem(localStorageName, JSON.stringify(data));