Query service hangs

Build : 6.5.0-2572

This issue wasn't seen in 6.5.0-2568

Query service hangs and then query service becomes unresponsive (you cannot connect to it via cbq)

Steps to reproduce :
1. 1-node cluster having kv+index+n1ql service
2. Create a bucket default and leave it empty
3. Run the following query :
SELECT COUNT FROM `default`

FYI: For consistent repro don't add semicolon at the end of select

Query hangs.

Could not find anything obvious from the logs related to this issue, but the above mentioned steps are 100% reproducible.