Remove unnecessary GetColumnCount() test in wxDataViewCtrl code

The presence of columns is already checked inside UpdateColumnSizes()
itself, so there is no need to do it before calling it too.

No real changes.

src/generic/datavgen.cpp

@@ -5272,7 +5272,7 @@ void wxDataViewCtrl::OnSize( wxSizeEvent &WXUNUSED(event) )
 
     // Update the last column size to take all the available space. Note that
     // this must be done after calling Layout() to update m_clientArea size.
-    if ( m_clientArea && GetColumnCount() )
+    if ( m_clientArea )
         m_clientArea->UpdateColumnSizes();
 
     AdjustScrollbars();