Fix reference leaks causing power consuption because of running IDLE.
Fix reference leaks causing power consuption because of running IDLE.

* src/modest-mail-operation.c (inbox_refreshed_cb): fix reference leaks in
  new_headers list, that could cause IDLE to be running after receiving a
  message, forever (fixes NB#131550).

community-ssu/modest,community-ssu/modest,community-ssu/modest,community-ssu/modest