event: Fix serialization of messages with colon but no space
event: Fix serialization of messages with colon but no space

For messages that contain either a colon **or** a space character, a
messagePrefix needs to be added to the serialized messages. Previously,
a message prefix was only added for messages containing a space
character. This causes messages which only contain a colon, but not a
space to be serialized incorrectly.

For example, prior to this commit a command like `PRIVMSG #foo ::)`,
which should send the message `:)` to the channel `#foo`, was
serialized as `PRIVMSG #foo :)` which only causes a `)` character to be
sent to the channel `#foo`.

lrstanley/girc