catch any exception on `singletonclass` #450

Job	Run time
ruby-versions / Generate Ruby versions	5s
test (3.0)	45s
test (3.1)	42s
test (3.2)	48s
test (3.3)	49s
test (debug)	1m 1s
test (3.4)	49s
test (head)	45s
	5m 44s

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