fix(problem): delete problem when zipfile is not valid

Author: zdszero

README.md

@@ -29,3 +29,5 @@ for more details check [onl-fe](https://github.com/OpenNetLab/OpenNetLab-Edu-FE)
 ```
 sudo nginx -c <absolute-dir-path>/nginx.conf
 ```
+
+- make sure [onl-library](https://github.com/OpenNetLab/OpenNetLab-Edu) is installed

problem/views/admin.py

@@ -48,6 +48,7 @@ def post(self, request):
         uploader = ZipFileUploader(request.FILES.get('file'), problem)
         valid = uploader.upload()
         if not valid:
+            problem.delete()
             return self.error(uploader.error_message)
 
         # create inexist tags