Check for m_treeCtrl!=NULL, [ wxwindows-Patches-1953459 ] wxGenericDirCtrl::SetFocus crash

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@53403 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/generic/dirctrlg.cpp

@@ -668,7 +668,8 @@ void wxGenericDirCtrl::SetFocus()
 {
     // we don't need focus ourselves, give it to the tree so that the user
     // could navigate it
-    m_treeCtrl->SetFocus();
+    if (m_treeCtrl)
+        m_treeCtrl->SetFocus();
 }
 
 void wxGenericDirCtrl::OnBeginEditItem(wxTreeEvent &event)