GtkComboBoxEntry doesn't return a 'match' on it's child entry's text
Submitted by Daniel Kasak
GtkComboBoxEntry only returns an iter if the ComboBox functionality is used. If the user ignores the ComboBox functionality and instead simply enters text into the child entry box, a 'match' is not registered even if the entered text matches an item in the model exactly, and when your try to get an iter, nothing is returned.
Or in an expert's words:
in gtk+/gtk/gtkcomboboxentry.c (http://cvs.gnome.org/viewcvs/gtk%2B/gtk/gtkcomboboxentry.c? rev=1.19&view=auto), the private function gtk_combo_box_entry_contents_changed, which is the handler for the "changed" signal on the entry (whenever you type something), calls gtk_combo_box_set_active (combo_box, -1).
that is, if you type something in, the code assumes you have selected none of the above. there is no attempt to match the entry's contents against the text column of the list store.