Fixes the error 500 for /auth/ endpoint (#3627)

Co-authored-by: rewhex <gitea@cluser.local>

src/plugins/api-server/backend/routes/auth.ts

@@ -75,9 +75,11 @@ export const register = (
       // SKIP CHECK
     }
 
-    setConfig({
-      authorizedClients: [...config.authorizedClients, id],
-    });
+    if (!config.authorizedClients.includes(id)) {
+      setConfig({
+        authorizedClients: [...config.authorizedClients, id],
+      });
+    }
 
     const token = await sign(
       {