BUG #15053: SIGSEGV - While executing query with cube agregator

The following bug has been logged on the website:

Bug reference:      15053
Logged by:          Orian Beltrame da Silva
Email address:      obeltrame@callixbrasil.com
PostgreSQL version: 9.6.3
Operating system:   Linux  4.9.0-4-amd64 #1 SMP Debian 4.9.65-3
Description:

Hi, 

the following postgres crash was generated during the execution of this
query:

 select
  freeswitch_bug_events.created_at::date,
  freeswitch_nodes."name",
  tenants."name",
  count(*) filter(where freeswitch_bug_events.event = 'call received'),
  count(*) filter(where freeswitch_bug_events.event = 'status changed')
from dev.freeswitch_bug_events
  join public.tenants on freeswitch_bug_events.tenant = tenants.id 
  join public.freeswitch_nodes on freeswitch_bug_events.node =
freeswitch_nodes.id
group by 
  cube (freeswitch_bug_events.created_at::date, freeswitch_nodes."name",
tenants."name" )

the query result is about 500k rows, so the developer was scrolling on the
result, using the dbeaver client, when the process on  the server crashed.

This crash puts the postgres in the recovery mode (a really nice feature!)
and after a few minutes the server was recovered and started to accpet new
connections.
I was enable to get a coredump of this process, if you people wants to
proccede to the investigation i can send the full core dump and a backup of
the tables involved.

Core was generated by `postgres: postgres db 192.168.1.165(54804) BIND
         '.
Program terminated with signal SIGSEGV, Segmentation fault.
#0  0x0000559ce4a520e4 in pfree ()
(gdb) bt
#0  0x0000559ce4a520e4 in pfree ()
#1  0x0000559ce4811e69 in ExecClearTuple ()
#2  0x0000559ce4811ebc in ExecResetTupleTable ()
#3  0x0000559ce4806349 in standard_ExecutorEnd ()
#4  0x0000559ce47cf8d3 in PortalCleanup ()
#5  0x0000559ce4a52842 in PortalDrop ()
#6  0x0000559ce4a52a50 in CreatePortal ()
#7  0x0000559ce49256ec in PostgresMain ()
#8  0x0000559ce469f2e2 in ?? ()
#9  0x0000559ce48c2dd1 in PostmasterMain ()
#10 0x0000559ce46a0497 in main ()