irc/bitlbee-discord: fix issue with glib >= 2.69

PR: 259072, 259257
Reported by: Corey Halpin <chalpin@cs.wisc.edu>,

	 	Arthur Pirika <arfy32@gmail.com> (maintainer)

MFH: 2021Q4 (bug fix)

(cherry picked from commit 637e1d7c317ebbec1d10c429142ec8c00a236a11)