Don't limit window size to (0, 0) in wxSizer if getting display size failed.

Don't limit window size to (0, 0) in wxSizer if getting display size failed.

It's possible that wxDisplay::GetClientArea() returns (0, 0) size indicating
that it failed. Don't set the maximal window size to (0, 0) in this case as
this prevents the user from seeing the window at all and just don't do
anything instead.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@69172 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775