wasapisink: fix missing unlock in case IAudioClient_Start fails

https://bugzilla.gnome.org/show_bug.cgi?id=796354
diff --git a/sys/wasapi/gstwasapisink.c b/sys/wasapi/gstwasapisink.c
index fc5a32f..7bff5d1 100644
--- a/sys/wasapi/gstwasapisink.c
+++ b/sys/wasapi/gstwasapisink.c
@@ -611,7 +611,8 @@
   GST_OBJECT_LOCK (self);
   if (self->client_needs_restart) {
     hr = IAudioClient_Start (self->client);
-    HR_FAILED_AND (hr, IAudioClient::Start, length = 0; goto beach);
+    HR_FAILED_AND (hr, IAudioClient::Start,
+      GST_OBJECT_UNLOCK (self); length = 0; goto beach);
     self->client_needs_restart = FALSE;
   }
   GST_OBJECT_UNLOCK (self);