fix(github): catch 409 empty

lib/platform/github/storage.js

@@ -361,6 +361,9 @@ class Storage {
         if (err.statusCode === 404) {
           throw new Error('repository-changed');
         }
+        if (err.statusCode === 409) {
+          throw new Error('empty');
+        }
         throw err;
       }
     }

lib/workers/repository/result.js

@@ -13,6 +13,7 @@ function processResult(config, res) {
     'not-found',
     'renamed',
     'uninitiated',
+    'empty',
   ];
   let status;
   // istanbul ignore next