State: gracefully handle 'dm' commands with non-existent channel names (fixes #21)
State: gracefully handle 'dm' commands with non-existent channel names (fixes #21)

This change makes it possible to run 'dm' commands for users with whom
you've never before chatted.  It just means the 'dm' command will do
nothing for those users.  This needs more work: create the relevant
channel and switch to it.  For now this change just avoids a crash.

matterhorn-chat/matterhorn,aisamanra/matterhorn