As it is currently implemented, insert_into_history can break the assumption that rl_history.entries has at least one element.

Since this function works with internal data of History, the logic of reading and writing the history file, should be moved to History. Let's call the new function in History something like append_reload_and_write (better names welcome). It would load the history file, append the entry and write the history file back. At the end it would check if entries has at least one element, and if not sets it to [''].