avoid unused variable warning with wxUSE_VALIDATORS==0

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_3_0_BRANCH@76350 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
initialize members in ctor, avoid int-to-bool warnings

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_3_0_BRANCH@76351 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
wxASSERT(false) --> wxFAIL

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_3_0_BRANCH@76352 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775