fix: check for email claim before skipping userinfo endpoint

backend/open_webui/utils/oauth.py

@@ -193,7 +193,7 @@ class OAuthManager:
             log.warning(f"OAuth callback error: {e}")
             raise HTTPException(400, detail=ERROR_MESSAGES.INVALID_CRED)
         user_data: UserInfo = token.get("userinfo")
-        if not user_data:
+        if not user_data or "email" not in user_data:
             user_data: UserInfo = await client.userinfo(token=token)
         if not user_data:
             log.warning(f"OAuth callback failed, user data is missing: {token}")