PONG breaks convention, breaks Thunderbird

[jesopo]

breaking convention:

• oragono (irc.hashbang.sh)
  :irc.hashbang.sh PONG asd
• charybdis (irc.alphachat.net)
  :irc-de1.alphachat.net PONG irc-de1.alphachat.net :asd
• inspircd (irc.tilde.chat)
  :institute.tilde.chat PONG institute.tilde.chat :asd
• unrealircd (irc.unrealircd.org)
  :irc1.unrealircd.org PONG irc1.unrealircd.org :asd
• ngircd (irc.w3.org)
  :public-irc.w3.org PONG public-irc.w3.org :asd

breaking Thunderbird:

leads to Thunderbird constantly deciding it has lost connection to the server and should reconnect

21:31 < Mateon1> Just for reference, I was connected to 8 other IRC servers at the time continuously for over a day (lost connection because my internet died for a couple minutes in the evening), this is the only server I'm having problems with.
21:31 < Mateon1> Also: prpl-irc: Unhandled IRC message:
21:31 < Mateon1> @time=2020-08-25T21:30:44.054Z :irc.hashbang.sh PONG _1598391044040
21:32 <~ryan> oh can it not handle PONGs that have a prefix?
21:32 < Mateon1> I could try digging into the source
21:32 < Mateon1> But seems like it
21:34 <~ryan> maybe it has a distinction between prefixed commands and non-prefixed commands that it's having issues with
21:36 < Mateon1> Hm, should be fine with the _ prefix: https://github.com/daniel-barrows/thunderbird/blob/6b0b38cdeeb0852950f15249f1b0e77f0bbddb05/chat/protocols/irc/ircBase.jsm#L287
21:37 <~ryan> hm.
21:37 <~ryan> one second.
21:37 < Mateon1> Ah, actually I missed some earlier debug output in the noise:
21:37 < Mateon1> prpl-irc: Error running command PONG with handler RFC 2812:
21:37 < Mateon1> {"rawMessage":"@time=2020-08-25T21:30:44.054Z :irc.hashbang.sh PONG _1598391044040","command":"PONG","params":["_1598391044040"],"origin":"irc.hashbang.sh","tags":{},"source":""}
21:37 < Mateon1> pongTime is undefined

this will be the issue, it's checking the index 1 param for starting with _
https://github.com/daniel-barrows/thunderbird/blob/6b0b38cdeeb0852950f15249f1b0e77f0bbddb05/chat/protocols/irc/ircBase.jsm#L289

[jesopo]

(I'm going to do a PR for this)