Don't pop up annoying message box in the drawing sample.

Don't pop up annoying message box in the drawing sample.

The rubber banding selection message box was shown even after a simple click,
i.e. when nothing was actually selected which was quite annoying, so don't do
this.

Also remove unnecessary casts and use wxLogMessage() instead of
wxString::Printf() + wxMessageBox().

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@67160 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775