The TestEncodeContainingArrayInvertedIndexSpans fails sporadically. This is due to unexpected results with randomly generated test cases.

The failue is:

index_encoding_test.go:466: For ARRAY['',''], expected unique=false, but got true

To reproduce, stress the test:

make stress PKG='./pkg/sql/rowenc' TESTS='TestEncodeContainingArrayInvertedIndexSpan
s' TESTTIMEOUT=30s

Example failure in CI: https://teamcity.cockroachdb.com/buildConfiguration/Cockroach_UnitTests/2482087?