Json Facets in version 7

[Chris Ulicny]

Hi all,

We are in the process of upgrading from version 6.3.0 to version 7.2.1 and
have found something that doesn't seem to work with the json facets any
more. The query is below

/select?q=*:*&wt=xml&indent=off&rows=0&fq=groupid:(4572
4573)+AND+gmttimestamp:[2018-08-05T00:00:00Z+TO+2018-08-07T00:59:59Z]&
json.facet={
    groupid_facet:{
        type:terms,
        field:groupid,
        limit:-1,
        facet:{sum_val1:"sum(value1)",sum_val2:"sum(val2)"}
    }
}

It currently returns: org.apache.solr.client.solrj.SolrServerException: No
live SolrServers available to handle this
request:[http://.../solr/collection_shard6_replica_n20,
http://.../solr/collection_shard6_replica_n22]

If I run the query directly against the "missing" shard with distrib=false,
we get the following NullPointerException and stack trace:
https://pastebin.com/UQK9je9G

However, the query runs fine in both cases if we change the limit to a
non-negative integer.

Is this a known issue, or some change between v6 and v7 that we missed?

Thanks,
Chris