Fix early return value from Handle Fetch (#1418)

Author: mfalken

docs/index.bs

@@ -2855,7 +2855,7 @@ spec: webappsec-referrer-policy; urlPrefix: https://w3c.github.io/webappsec-refe
           * |request| is a [=subresource request=] and |registration| is [=stale=].
       1. If the result of running the [=Should Skip Event=] algorithm with "fetch" and |activeWorker| is true, then:
           1. If |shouldSoftUpdate| is true, then [=in parallel=] run the [=Soft Update=] algorithm with |registration|.
-          1. Return.
+          1. Return null.
       1. If |activeWorker|'s <a>state</a> is *activating*, wait for |activeWorker|'s <a>state</a> to become *activated*.
       1. Invoke <a>Run Service Worker</a> algorithm with |activeWorker| as the argument.
       1. <a>Queue a task</a> |task| to run the following substeps:

docs/v1/index.bs

@@ -2652,7 +2652,7 @@ spec: webappsec-referrer-policy; urlPrefix: https://w3c.github.io/webappsec-refe
           * |request| is a [=subresource request=] and |registration| is [=stale=].
       1. If the result of running the [=Should Skip Event=] algorithm with "fetch" and |activeWorker| is true, then:
           1. If |shouldSoftUpdate| is true, then [=in parallel=] run the [=Soft Update=] algorithm with |registration|.
-          1. Return.
+          1. Return null.
       1. If |activeWorker|'s <a>state</a> is *activating*, wait for |activeWorker|'s <a>state</a> to become *activated*.
       1. Invoke <a>Run Service Worker</a> algorithm with |activeWorker| as the argument.
       1. <a>Queue a task</a> |task| to run the following substeps: