[AddOn] [Chatmon] Server system message causes error message

[koalatytimekoala]

The server system messages informing players when maintenance is coming and to logout before maintenance begins causes Chatmon to print an error ".../Chatmon.lua:85 attempt to index field '?' (a nil value)

[z16]

@Nifim Looks like system messages aren't handled. Will need to get an ID for this.