richmemo: win32 fix for theme border drawing. #28269, based on the patch by Andrey Korol

git-svn-id: https://svn.code.sf.net/p/lazarus-ccr/svn@4190 8e941d3f-bd1b-0410-a28a-d453659cc2b4

components/richmemo/win32/win32richmemo.pas

@@ -1291,6 +1291,7 @@ begin
   Handled:=(GetWindowLong(AWindow, GWL_EXSTYLE) and WS_EX_CLIENTEDGE <> 0) and (ThemeServices.ThemesEnabled);
   if Handled then begin
     // Paint into this DC
+    WindowProc(AWindow, WM_NCPAINT, WParam, LParam);
     ThemeServices.PaintBorder(RichMemo, True);
     Result := 0;
   end;