Prove `map_fmap_empty_inv`.

6 jobs for master in 18 minutes and 6 seconds (queued for 1 second)
Status Job ID Name Coverage
  Build
passed #9360
fp
build-coq.8.6.0

00:11:44

passed #9359
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build-coq.8.6.1

00:10:35

passed #9358
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build-coq.8.7.0

00:10:20

passed #9357
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build-coq.8.7.1

00:10:23

passed #9356
fp-timing
build-coq.8.7.2

00:07:17

passed #9355
fp
build-coq.dev

00:18:06