Server crashed with dense_rank on partition table.

I am getting server crash with below query.

CREATE TABLE pagg_tab (a int, b int, c text) PARTITION BY LIST(c);
CREATE TABLE pagg_tab_p1 PARTITION OF pagg_tab FOR VALUES IN ('0000', '0001', '0002', '0003');
CREATE TABLE pagg_tab_p2 PARTITION OF pagg_tab FOR VALUES IN ('0004', '0005', '0006', '0007');
CREATE TABLE pagg_tab_p3 PARTITION OF pagg_tab FOR VALUES IN ('0008', '0009', '0010', '0011');
INSERT INTO pagg_tab SELECT i % 20, i % 30, to_char(i % 12, 'FM0000') FROM generate_series(0, 36) i;
ANALYZE pagg_tab;
SELECT dense_rank(b) WITHIN GROUP (ORDER BY a) FROM pagg_tab GROUP BY b ORDER BY 1;

postgres=# SELECT dense_rank(b) WITHIN GROUP (ORDER BY a) FROM pagg_tab GROUP BY b ORDER BY 1;
server closed the connection unexpectedly
    This probably means the server terminated abnormally
    before or while processing the request.
The connection to the server was lost. Attempting reset: Failed.

logfile have this

2018-06-12 21:29:54.930 IST [69580] STATEMENT:  drop table pagg_tab;
TRAP: BadArgument("!(((context) != ((void *)0) && (((((const Node*)((context)))->type) == T_AllocSetContext) || ((((const Node*)((context)))->type) == T_SlabContext) || ((((const Node*)((context)))->type) == T_GenerationContext))))", File: "mcxt.c", Line: 775)
2018-06-12 21:29:55.552 IST [69571] LOG:  server process (PID 69580) was terminated by signal 6: Aborted
2018-06-12 21:29:55.552 IST [69571] DETAIL:  Failed process was running: SELECT dense_rank(b) WITHIN GROUP (ORDER BY a) FROM pagg_tab GROUP BY b ORDER BY 1;
2018-06-12 21:29:55.552 IST [69571] LOG:  terminating any other active server processes

and here is core file content

Loaded symbols for /lib64/libnss_files.so.2
Core was generated by `postgres: edb postgres [local] SELECT                   '.
Program terminated with signal 6, Aborted.
#0  0x0000003dd2632495 in raise (sig=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:64
64      return INLINE_SYSCALL (tgkill, 3, pid, selftid, sig);
Missing separate debuginfos, use: debuginfo-install keyutils-libs-1.4-5.el6.x86_64 krb5-libs-1.10.3-65.el6.x86_64 libcom_err-1.41.12-23.el6.x86_64 libselinux-2.0.94-7.el6.x86_64 openssl-1.0.1e-57.el6.x86_64 zlib-1.2.3-29.el6.x86_64
(gdb) bt
#0  0x0000003dd2632495 in raise (sig=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:64
#1  0x0000003dd2633c75 in abort () at abort.c:92
#2  0x0000000000a32622 in ExceptionalCondition (
    conditionName=0xc99320 "!(((context) != ((void *)0) && (((((const Node*)((context)))->type) == T_AllocSetContext) || ((((const Node*)((context)))->type) == T_SlabContext) || ((((const Node*)((context)))->type) == T_Generatio"..., errorType=0xc99312 "BadArgument", fileName=0xc993f5 "mcxt.c", lineNumber=775) at assert.c:54
#3  0x0000000000a6be3a in MemoryContextAlloc (context=0x134a708, size=8) at mcxt.c:775
#4  0x0000000000a6d0a6 in MemoryContextStrdup (context=0x134a708, string=0xc60413 "integer") at mcxt.c:1153
#5  0x0000000000a6d0e9 in pstrdup (in=0xc60413 "integer") at mcxt.c:1163
#6  0x0000000000927328 in format_type_extended (type_oid=23, typemod=-1, flags=0) at format_type.c:224
#7  0x00000000009275c4 in format_type_be (type_oid=23) at format_type.c:330
#8  0x00000000006d41ed in CheckVarSlotCompatibility (slot=0x134a6a8, attnum=1, vartype=23) at execExprInterp.c:1883
#9  0x00000000006d4062 in CheckExprStillValid (state=0x1388370, econtext=0x134a6a8) at execExprInterp.c:1823
#10 0x00000000006d3f5e in ExecInterpExprStillValid (state=0x1388370, econtext=0x134a6a8, isNull=0x7ffe988f3907) at execExprInterp.c:1780
#11 0x000000000098a116 in ExecEvalExprSwitchContext (state=0x1388370, econtext=0x134a6a8, isNull=0x7ffe988f3907) at ../../../../src/include/executor/executor.h:303
#12 0x000000000098a191 in ExecQual (state=0x1388370, econtext=0x134a6a8) at ../../../../src/include/executor/executor.h:372
#13 0x000000000098a1e3 in ExecQualAndReset (state=0x1388370, econtext=0x134a6a8) at ../../../../src/include/executor/executor.h:389
#14 0x000000000098cb96 in hypothetical_dense_rank_final (fcinfo=0x7ffe988f3a40) at orderedsetaggs.c:1389
#15 0x00000000006f3a5d in finalize_aggregate (aggstate=0x1368f98, peragg=0x1382a38, pergroupstate=0x1382be8, resultVal=0x13829f8, resultIsNull=0x1382a18) at nodeAgg.c:965
#16 0x00000000006f3ff0 in finalize_aggregates (aggstate=0x1368f98, peraggs=0x1382a38, pergroup=0x1382be8) at nodeAgg.c:1172
#17 0x00000000006f516a in agg_retrieve_direct (aggstate=0x1368f98) at nodeAgg.c:1887
#18 0x00000000006f4a6d in ExecAgg (pstate=0x1368f98) at nodeAgg.c:1551
#19 0x0000000000718972 in ExecProcNode (node=0x1368f98) at ../../../src/include/executor/executor.h:237
#20 0x0000000000718abe in ExecSort (pstate=0x1368e80) at nodeSort.c:107
#21 0x00000000006e6b26 in ExecProcNodeFirst (node=0x1368e80) at execProcnode.c:445
#22 0x00000000006dbd61 in ExecProcNode (node=0x1368e80) at ../../../src/include/executor/executor.h:237
#23 0x00000000006de71b in ExecutePlan (estate=0x1368c68, planstate=0x1368e80, use_parallel_mode=false, operation=CMD_SELECT, sendTuples=true, numberTuples=0,
    direction=ForwardScanDirection, dest=0x137a928, execute_once=true) at execMain.c:1726
#24 0x00000000006dc34b in standard_ExecutorRun (queryDesc=0x1354318, direction=ForwardScanDirection, count=0, execute_once=true) at execMain.c:363
#25 0x00000000006dc167 in ExecutorRun (queryDesc=0x1354318, direction=ForwardScanDirection, count=0, execute_once=true) at execMain.c:306
#26 0x00000000008cadd2 in PortalRunSelect (portal=0x12f0c28, forward=true, count=0, dest=0x137a928) at pquery.c:932
#27 0x00000000008caa60 in PortalRun (portal=0x12f0c28, count=9223372036854775807, isTopLevel=true, run_once=true, dest=0x137a928, altdest=0x137a928,
    completionTag=0x7ffe988f43a0 "") at pquery.c:773
#28 0x00000000008c4a37 in exec_simple_query (query_string=0x128b798 "SELECT dense_rank(b) WITHIN GROUP (ORDER BY a) FROM pagg_tab GROUP BY b ORDER BY 1;") at postgres.c:1122
#29 0x00000000008c8d07 in PostgresMain (argc=1, argv=0x12b52a0, dbname=0x12b5100 "postgres", username=0x1288298 "edb") at postgres.c:4153
#30 0x00000000008264f7 in BackendRun (port=0x12ad060) at postmaster.c:4361
#31 0x0000000000825c65 in BackendStartup (port=0x12ad060) at postmaster.c:4033
#32 0x0000000000822047 in ServerLoop () at postmaster.c:1706
#33 0x0000000000821979 in PostmasterMain (argc=3, argv=0x12861f0) at postmaster.c:1379
#34 0x0000000000748bc4 in main (argc=3, argv=0x12861f0) at main.c:228