Don't constantly reload comctl32.dll in wxTreeCtrl::MSWOnNotify().

The "loaded" flag was never set to true, so we kept reloading the DLL on every
callback.

Do set the flag after loading it successfully.

Closes #14512.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@72185 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/msw/treectrl.cpp

@@ -3513,7 +3513,10 @@ bool wxTreeCtrl::MSWOnNotify(int idCtrl, WXLPARAM lParam, WXLPARAM *result)
                             {
                                 wxLoadedDLL dllComCtl32(wxT("comctl32.dll"));
                                 if ( dllComCtl32.IsLoaded() )
+                                {
                                     wxDL_INIT_FUNC(s_pfn, ImageList_Copy, dllComCtl32);
+                                    loaded = true;
+                                }
                             }
 
                             if ( !s_pfnImageList_Copy )