Ensure passNextWrite is reset after passing it
* src/mailitem-events.cpp (Write): After passing a write because of passNextWrite ensure that it is set back.
This is usually not a problem because the passWrite happens
only after closing with discard changes and usually an unload
follows. But if the mail is open multiple times it could
happen that the state here was broken.
- GnuPG-Bug-Id: T4622