DoGetBestSize may be called before m_text and m_choice are set,

so check


git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@27896 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/mac/carbon/combobox.cpp

@@ -205,6 +205,8 @@ wxComboBox::~wxComboBox()
 
 wxSize wxComboBox::DoGetBestSize() const
 {
+    if (!m_choice || !m_text)
+        return GetSize();
     wxSize size = m_choice->GetBestSize();
     
     if ( m_text != NULL )