missing empty cs check for cs_sum cause backend crash

[amutu]

postgres=# select cs_filter((k1=cs_const('xxx',16)) & (k3=cs_const('dse',16)) & (k5 = cs_const('ab',16)),v4) from test2_get();

cs_filter

int8:{}
(1 row)

Time: 9364.218 ms
postgres=# select cs_sum(cs_filter((k1=cs_const('xxx',16)) & (k3=cs_const('dse',16)) & (k5 = cs_const('ab',16)),v4)) from test2_get();
The connection to the server was lost. Attempting reset: Failed.
Time: 953.200 ms
!>

[knizhnik]

Thank you once again for reporting the problem.
The bug was in parallel executor which cause crash in case of empty result.
Fixed.