fix(aws): Minor leak on empty_payload_hex when canonical request build fails

Signed-off-by: Arbin <[email protected]>

Author: kalavt

src/aws/flb_aws_msk_iam.c

@@ -570,6 +570,9 @@ static flb_sds_t build_msk_iam_payload(struct flb_aws_msk_iam *config,
     if (session_token_enc) {
         flb_sds_destroy(session_token_enc);
     }
+    if (empty_payload_hex) {
+        flb_sds_destroy(empty_payload_hex);
+    }
 
     return NULL;
 }