Check if composer is already closing before asking about closing
Check if composer is already closing before asking about closing

The composer can hide itself while the draft manager is in the process
of closing up.  If we try to close that composer again, it should
automatically return PENDING_CLOSE instead of asking the user what to
do.

jimbonator/geary,tshikaboom/geary,mjog/geary,emersion/geary,githubnemo/geary,martinra/geary,AtticHacker/geary,jimbonator/geary,robol/geary,tshikaboom/geary,martinra/geary,martinra/geary,mjog/geary,jimbonator/geary,emersion/geary,githubnemo/geary,aatishnn/geary,aatishnn/geary,robol/geary,mjog/geary,glebihan/geary,glebihan/geary,emersion/geary,githubnemo/geary,glebihan/geary,AtticHacker/geary,tshikaboom/geary,AtticHacker/geary,aatishnn/geary,robol/geary