Bug 1569772 - Release load group on main thread in win/nsIconChannel r=tnikkel

Differential Revision: https://phabricator.services.mozilla.com/D39795

--HG--
extra : moz-landing-system : lando

image/decoders/icon/win/nsIconChannel.cpp

@@ -170,6 +170,10 @@ nsIconChannel::~nsIconChannel() {
     NS_ReleaseOnMainThreadSystemGroup("nsIconChannel::mLoadInfo",
                                       mLoadInfo.forget());
   }
+  if (mLoadGroup) {
+    NS_ReleaseOnMainThreadSystemGroup("nsIconChannel::mLoadGroup",
+                                      mLoadGroup.forget());
+  }
 }
 
 NS_IMPL_ISUPPORTS(nsIconChannel, nsIChannel, nsIRequest, nsIRequestObserver,