Remove asserts in wxMSW::wxTLW::SetIcons() and always set some icon.

Remove asserts in wxMSW::wxTLW::SetIcons() and always set some icon.

In practice having the icons of the exact size for all versions of Windows is
not always possible, there are just too many of them. So set the icon of the
most suitable size if no exact match is found instead of asserting in this
case.

See #11146.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@65084 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775