don't clear value index in SetStringValue() if the value is invalid (patch 1905695)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_2_8_BRANCH@52251 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/generic/odcombo.cpp

@@ -632,10 +632,11 @@ void wxVListBoxComboPopup::SetStringValue( const wxString& value )
 {
     int index = m_strings.Index(value);
 
+    if ( index >= 0 && index < (int)wxVListBox::GetItemCount() )
+    {
         m_value = index;
-
-    if ( index >= -1 && index < (int)wxVListBox::GetItemCount() )
         wxVListBox::SetSelection(index);
+    }
 }
 
 void wxVListBoxComboPopup::CalcWidths()