Don't assert when we get wxBG_STYLE_TRANSPARENT.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@62650 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/osx/window_osx.cpp

@@ -1875,6 +1875,7 @@ bool wxWindowMac::MacDoRedraw( long time )
             break;
 
         case wxBG_STYLE_PAINT:
+        case wxBG_STYLE_TRANSPARENT:
             // nothing to do, user-defined EVT_PAINT handler will overwrite the
             // entire window client area
             break;