Clear selection when generic wxDataViewCtrl is cleared.

Selection could retain its old value and become invalid after calling Reset()
before.

Closes #12559.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@65821 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/generic/datavgen.cpp

@@ -2094,6 +2094,7 @@ bool wxDataViewMainWindow::ValueChanged( const wxDataViewItem & item, unsigned i
 bool wxDataViewMainWindow::Cleared()
 {
     DestroyTree();
+    m_selection.Clear();
 
     SortPrepare();
     BuildTree( GetOwner()->GetModel() );