fix(boxsdkgen): fix RetryAfter function when there's no Retry-After header (box/box-codegen#903) (#1250)

Co-authored-by: box-sdk-build <box-sdk-build@box.com>

Author: box-sdk-build

.codegen.json

@@ -1 +1 @@
-{ "engineHash": "3d9d391", "specHash": "31c41d5", "version": "4.2.0" }
+{ "engineHash": "f97463c", "specHash": "31c41d5", "version": "4.2.0" }

src/sdk-gen/networking/retries.ts

@@ -118,7 +118,9 @@ export class BoxRetryStrategy implements RetryStrategy {
     attemptNumber: number
   ): number {
     const retryAfterHeader: undefined | string =
-      fetchResponse.headers['Retry-After'];
+      'Retry-After' in fetchResponse.headers
+        ? fetchResponse.headers['Retry-After']
+        : void 0;
     if (!(retryAfterHeader == void 0)) {
       return parseFloat(retryAfterHeader!) as number;
     }