Endless WM_PAINT loop fix

[Alexandre Julliard]

Rein Klazes <rklazes at xs4all.nl> writes:

> Changelog:
> 	windows		: painting.c
> 	If RedrawWindow is called with the RDW_INVALIDATE flag, if the 	
> 	UpdateRgn parameter is a NULLREGION and the Window has no update
> 	region yet, ignore the call.

This should be integrated with the update region calculations, we
shouldn't add such special cases outside of the main code.

-- 
Alexandre Julliard
julliard at winehq.com