fix(nextjs): Gracefully handle undefined beforeFiles in rewrites (#7649)

Co-authored-by: Luca Forstner <[email protected]>

Author: bertho-zero

packages/nextjs/src/config/types.ts

@@ -53,9 +53,9 @@ export type NextConfigObject = {
   rewrites?: () => Promise<
     | NextRewrite[]
     | {
-        beforeFiles: NextRewrite[];
-        afterFiles: NextRewrite[];
-        fallback: NextRewrite[];
+        beforeFiles?: NextRewrite[];
+        afterFiles?: NextRewrite[];
+        fallback?: NextRewrite[];
       }
   >;
 };

packages/nextjs/src/config/withSentryConfig.ts

@@ -104,7 +104,7 @@ function setUpTunnelRewriteRules(userNextConfig: NextConfigObject, tunnelPath: s
     } else {
       return {
         ...originalRewritesResult,
-        beforeFiles: [injectedRewrite, ...originalRewritesResult.beforeFiles],
+        beforeFiles: [injectedRewrite, ...(originalRewritesResult.beforeFiles || [])],
       };
     }
   };