Comment 1 for bug 1214432

The appears when a proposal is selected, selecting a proposal generates the error. do_get_start_iter() is called just before the C code takes over, and it calls gtk_text_buffer_get_iter_at_mark() that guarantees a new iter. Maybe the completion was initialized with a stale iter, but since the plugin uses marks to indicate where the cursor and word is in the doc, it seem unlikely that code or user could have changed the document.