panic during update statistics of nested array index

UPSERT INTO default VALUES ("book1", { "type":"book", "author": "James", "rev": 2, "year": 2020, "name": "book 1", "description": "book 1 description", "isbn": 1, "chapters": [ {"num": 1, "name": "chapter 1", "description": "chapter 1 description", "pages" : [ { "num":1, "name":"page 1", "description": "page 1 description"}, { "num":2, "name":"page 2", "description": "page 2 description"} ]}]});

CREATE INDEX ixf20 ON default(isbn, author, DISTINCT ARRAY (DISTINCT ARRAY pg.num FOR pg IN ch.pages END) FOR ch IN chapters END, year, name) WHERE type = "book";

update statistics default index (ixf20);

panic: runtime error: comparing uncomparable type value.sliceValue

goroutine 434 [running]:

github.com/couchbase/query-ee/histogram.genHistogram(0xc003fdc5d0, 0x21, 0x26927a8, 0xc000b29b30, 0x1, 0x1, 0x3ff0000000000000, 0x0, 0x0, 0xc003e8b910, ...)

        /home/couchbase/jenkins/workspace/couchbase-server-unix/goproj/src/github.com/couchbase/query-ee/histogram/histogram.go:362 +0xe65

github.com/couchbase/query-ee/histogram.GetHistogram(0xc003fdc5d0, 0x21, 0x26927a8, 0xc0003c1ea0, 0x1, 0x1, 0x3ff0000000000000, 0x0, 0x0, 0xc003e8b910, ...)

        /home/couchbase/jenkins/workspace/couchbase-server-unix/goproj/src/github.com/couchbase/query-ee/histogram/histogram.go:546 +0x11f

github.com/couchbase/query-ee/updstat.doUpdateStatistics(0x2682bb0, 0xc000b81380, 0x263ada0, 0xc0040f4240, 0xc003e27560, 0x6, 0x6, 0x0, 0x1, 0xc000fcbab8, ...)

        /home/couchbase/jenkins/workspace/couchbase-server-unix/goproj/src/github.com/couchbase/query-ee/updstat/upd_statistics.go:451 +0x1317

github.com/couchbase/query-ee/updstat.(*DefaultStatUpdater).UpdateStatistics(0xc000080fd0, 0x2682bb0, 0xc000b81380, 0xc000c1e450, 0x1, 0x1, 0xc003e27560, 0x6, 0x6, 0x0, ...)

        /home/couchbase/jenkins/workspace/couchbase-server-unix/goproj/src/github.com/couchbase/query-ee/updstat/upd_statistics.go:291 +0x88e

created by github.com/couchbase/query/execution.(*UpdateStatistics).RunOnce.func1

        /home/couchbase/jenkins/workspace/couchbase-server-unix/goproj/src/github.com/couchbase/query/execution/update_stat.go:87 +0x365