gdi32: Add support for the null brush.

dlls/gdi32/dibdrv/objects.c

@@ -1062,6 +1062,11 @@ static BOOL pattern_brush(dibdrv_physdev *pdev, int num, RECT *rects)
     return TRUE;
 }
 
+static BOOL null_brush(dibdrv_physdev *pdev, int num, RECT *rects)
+{
+    return TRUE;
+}
+
 void update_brush_rop( dibdrv_physdev *pdev, INT rop )
 {
     pdev->brush_rop = rop;
@@ -1101,6 +1106,11 @@ HBRUSH CDECL dibdrv_SelectBrush( PHYSDEV dev, HBRUSH hbrush )
         pdev->defer &= ~DEFER_BRUSH;
         break;
 
+    case BS_NULL:
+        pdev->brush_rects = null_brush;
+        pdev->defer &= ~DEFER_BRUSH;
+        break;
+
     case BS_DIBPATTERN:
     {
         BITMAPINFOHEADER *bi = GlobalLock((HGLOBAL)logbrush.lbHatch);