Patch from Bo, adapt generic code to new API, add GetItemRect and HitTest

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@48223 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/common/datavcmn.cpp

@@ -683,6 +683,9 @@ bool wxDataViewCtrlBase::ClearColumns()
 
 wxDataViewColumn* wxDataViewCtrlBase::GetColumn( unsigned int pos )
 {
+    if( pos >= m_cols.GetCount() )
+        return NULL;
+
     return (wxDataViewColumn*) m_cols[ pos ];
 }