Sometimes the Android runtime kills off the Bote process to save memory, and
recreates it when the user next opens it. If the user was on an Activity that
was not EmailListActivity, then when recreated the I2P system vars would not be
set, and the first call to I2PBote.getInstance() would create an instance with
invalid paths. This was non-fatal - killing Bote and restarting it would fix
the problem - but was bad UX, because from the user's PoV all their emails and
data had disappeared.
