fix exception handling

app.py

@@ -50,9 +50,9 @@ def generate_boilerplate(
         }
 
         if not gh_token:
-            gr.Error("Please enter your GitHub token!")
+            raise gr.Error("Please enter your GitHub token!")
         if not gh_repo_name:
-            gr.Error("Please enter your GitHub repository name!")
+            raise gr.Error("Please enter your GitHub repository name!")
 
         github_repo_creator_kwargs = {
             "token": gh_token,