Provide a fallback text colour for text in wxRTC


git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74941 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
Fix default size of un-resizable windows, broken in r74685
see #14870
closes #15549


git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74942 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775