fix: Remove non-null assertion in withTimeout by initializing timeoutId with undefined

Author: torosent

packages/durabletask-js/src/utils/backoff.util.ts

@@ -213,7 +213,7 @@ export async function withTimeout<T>(
   timeoutMs: number,
   timeoutMessage = "Operation timed out",
 ): Promise<T> {
-  let timeoutId: ReturnType<typeof setTimeout>;
+  let timeoutId: ReturnType<typeof setTimeout> | undefined;
 
   const timeoutPromise = new Promise<never>((_, reject) => {
     timeoutId = setTimeout(() => reject(new Error(timeoutMessage)), timeoutMs);
@@ -222,6 +222,8 @@ export async function withTimeout<T>(
   try {
     return await Promise.race([promise, timeoutPromise]);
   } finally {
-    clearTimeout(timeoutId!);
+    if (timeoutId !== undefined) {
+      clearTimeout(timeoutId);
+    }
   }
 }