Made bot quit when sock_file.readline() returns ''

If sock_file.readline() returns '', the socket has closed. This change
makes the bot quit when this has occurred. This is useful when the IRC
network goes down and you want the bot to rejoin when it has gone up
again, instead of having the bot hang.

 utils/irc.py | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)