fab output window: properly show Glib errors #1496

Job	Run time
stylecheck	25s
build-pr-review	5m 28s
build-arch (all)	22m 8s
build-debug	24m 40s
build-arch (horizon.so)	6m 24s
build (ubuntu:focal, g++, gcc, all)	23m 11s
build-opensuse (all)	21m 15s
build (ubuntu:focal, g++, gcc, horizon.so)	7m 0s
build (ubuntu:jammy, g++, gcc, all)	27m 59s
build-opensuse (horizon.so)	5m 57s
build (ubuntu:jammy, g++, gcc, horizon.so)	6m 8s
build (ubuntu:lunar, g++, gcc, all)	21m 39s
build (ubuntu:lunar, g++, gcc, horizon.so)	7m 11s
build (debian:bullseye, g++, gcc, all)	19m 20s
build (debian:bullseye, g++, gcc, horizon.so)	6m 34s
build (debian:bookworm, clang, clang, all)	19m 23s
build (debian:bookworm, clang, clang, horizon.so)	7m 46s
build (debian:bookworm, g++, gcc, all)	22m 25s
build (debian:bookworm, g++, gcc, horizon.so)	8m 7s
	4h 23m 0s

Provide feedback