Make `withErrors` exception safe #330

Job	Run time
cabal-check (9.6.6, 3.10.3.0, ubuntu-latest)	2m 5s
stylish-haskell (9.6.6, 3.12.1.0, ubuntu-latest)	12m 49s
build (8.10.7, 3.12.1.0, ubuntu-latest)	5m 25s
cabal-fmt (9.6.6, 3.12.1.0, ubuntu-latest)	2m 43s
build (8.10.7, 3.12.1.0, windows-latest)	7m 42s
build (8.10.7, 3.12.1.0, macOS-13)	11m 42s
build (9.2.8, 3.12.1.0, ubuntu-latest)	4m 43s
build (9.2.8, 3.12.1.0, windows-latest)	7m 35s
build (9.2.8, 3.12.1.0, macOS-13)	8m 22s
build (9.4.8, 3.12.1.0, ubuntu-latest)	5m 19s
build (9.4.8, 3.12.1.0, windows-latest)	7m 12s
build (9.4.8, 3.12.1.0, macOS-13)	10m 40s
build (9.6.6, 3.12.1.0, ubuntu-latest)	5m 31s
build (9.6.6, 3.12.1.0, windows-latest)	7m 2s
build (9.6.6, 3.12.1.0, macOS-13)	10m 17s
build (9.8.2, 3.12.1.0, ubuntu-latest)	5m 49s
build (9.8.2, 3.12.1.0, windows-latest)	8m 28s
build (9.8.2, 3.12.1.0, macOS-13)	14m 34s
build (9.10.1, 3.12.1.0, ubuntu-latest)	3m 54s
build (9.10.1, 3.12.1.0, windows-latest)	7m 59s
build (9.10.1, 3.12.1.0, macOS-13)	13m 48s
build (9.6.6, 3.12.1.0, ubuntu-latest, no-debug)	5m 26s
	2h 49m 5s

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