Port #62483: Disable conditional exports fallbacks on null values (#2… #9374

Job	Run time
format	1m 49s
lint (ubuntu-latest)	5m 31s
tidy	1m 18s
generate	10m 56s
smoke	5m 29s
extension	46s
misc	1m 25s
build	3m 37s
lint (windows-latest)	11m 7s
test (noembed)	8m 55s
test (concurrent test programs)	11m 34s
test (no submodules)	8m 0s
test (windows-latest)	20m 13s
test (ubuntu-latest)	12m 4s
test (macos-latest)	14m 34s
test (race mode)	17m 58s
lint (noembed)	6m 9s
required	3s
	2h 21m 28s

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