fix: use optional chaining to fix lint errors (#1485)

lib/ai/tools/request-suggestions.ts

@@ -31,7 +31,7 @@ export const requestSuggestions = ({
     execute: async ({ documentId }) => {
       const document = await getDocumentById({ id: documentId });
 
-      if (!document || !document.content) {
+      if (!document?.content) {
         return {
           error: "Document not found",
         };