Fix double-callback-call crash in //components/cast_channel/

Fix use-after-move (potential) bugs found by the
"bugprone-use-after-move" clang-tidy check.

Bug: 1122844
Change-Id: I1b8ae11a95b384ad0c086c0fe62a2187338f4ab8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2382073Reviewed-by: mark a. foltz <mfoltz@chromium.org>
Commit-Queue: mark a. foltz <mfoltz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#804454}

components/cast_channel/cast_message_handler.cc

@@ -311,6 +311,7 @@ void CastMessageHandler::SendSetVolumeRequest(int channel_id,
   if (!socket) {
     DVLOG(2) << __func__ << ": socket not found: " << channel_id;
     std::move(callback).Run(Result::kFailed);
+    return;
   }
 
   auto* requests = GetOrCreatePendingRequests(channel_id);