Select with intersect & union all from reference table (assertion) crashes at ruleutils

```sql
CREATE TABLE INT8_TBL(q1 int8, q2 int8);
SELECT create_reference_table('INT8_TBL');
(((
SELECT q1 FROM int8_tbl
INTERSECT
SELECT q2 FROM int8_tbl ORDER BY 1
)))
UNION ALL
SELECT q2 FROM int8_tbl;
```

Above select crashes due to assertion failure with below backtrace:

```c
#2 0x0000000000aae380 in ExceptionalCondition (conditionName=0x7f5ffa87d158 "!(subquery->setOperations == ((void *)0))",
errorType=0x7f5ffa87ca81 "FailedAssertion", fileName=0x7f5ffa87caf1 "deparser/ruleutils_12.c", lineNumber=2573) at assert.c:54
#3 0x00007f5ffa7cf8dd in get_setop_query (setOp=0x1df7a68, query=0x1de7220, context=0x7ffeb0977df0, resultDesc=0x0) at deparser/ruleutils_12.c:2573
#4 0x00007f5ffa7cfa80 in get_setop_query (setOp=0x1df7a10, query=0x1de7220, context=0x7ffeb0977df0, resultDesc=0x0) at deparser/ruleutils_12.c:2625
#5 0x00007f5ffa7cebff in get_select_query_def (query=0x1de7220, context=0x7ffeb0977df0, resultDesc=0x0) at deparser/ruleutils_12.c:2150
#6 0x00007f5ffa7ce64a in get_query_def_extended (query=0x1de7220, buf=0x1e09bd8, parentnamespace=0x0, distrelid=0, shardid=0, resultDesc=0x0,
prettyFlags=0, wrapColumn=0, startIndent=0) at deparser/ruleutils_12.c:1964
#7 0x00007f5ffa7ce48c in get_query_def (query=0x1de7220, buf=0x1e09bd8, parentnamespace=0x0, resultDesc=0x0, prettyFlags=0, wrapColumn=0, startIndent=0)
at deparser/ruleutils_12.c:1907
#8 0x00007f5ffa7cb2d4 in pg_get_query_def (query=0x1de7220, buffer=0x1e09bd8) at deparser/ruleutils_12.c:457
#9 0x00007f5ffa8099db in DeparseTaskQuery (task=0x1e08420, query=0x1de7220) at planner/deparse_shard_query.c:499
#10 0x00007f5ffa809b20 in TaskQueryString (task=0x1e08420) at planner/deparse_shard_query.c:564
#11 0x00007f5ffa7e833d in ExecuteLocalTaskListExtended (taskList=0x1e31590, orig_paramListInfo=0x0, distributedPlan=0x1e06ee8, defaultTupleDest=0x1e31300,
isUtilityCommand=false) at executor/local_executor.c:281
#12 0x00007f5ffa7dcd23 in RunLocalExecution (scanState=0x1d73270, execution=0x1e31338) at executor/adaptive_executor.c:825
#13 0x00007f5ffa7dcb52 in AdaptiveExecutor (scanState=0x1d73270) at executor/adaptive_executor.c:751
#14 0x00007f5ffa7e1f53 in CitusExecScan (node=0x1d73270) at executor/citus_custom_scan.c:224
#15 0x0000000000732cc9 in ExecCustomScan (pstate=0x1d73270) at nodeCustom.c:116
#16 0x000000000071a5d6 in ExecProcNodeFirst (node=0x1d73270) at execProcnode.c:445
#17 0x000000000070f414 in ExecProcNode (node=0x1d73270) at ../../../src/include/executor/executor.h:239
#18 0x0000000000711c4f in ExecutePlan (estate=0x1d72f28, planstate=0x1d73270, use_parallel_mode=false, operation=CMD_SELECT, sendTuples=true,
numberTuples=0, direction=ForwardScanDirection, dest=0x1e097d8, execute_once=true) at execMain.c:1646
#19 0x000000000070fa51 in standard_ExecutorRun (queryDesc=0x1cb0c58, direction=ForwardScanDirection, count=0, execute_once=true) at execMain.c:364
#20 0x00007f5ffa7ea6e7 in CitusExecutorRun (queryDesc=0x1cb0c58, direction=ForwardScanDirection, count=0, execute_once=true)
at executor/multi_executor.c:202
#21 0x000000000070f874 in ExecutorRun (queryDesc=0x1cb0c58, direction=ForwardScanDirection, count=0, execute_once=true) at execMain.c:306
#22 0x0000000000924d35 in PortalRunSelect (portal=0x1cf87d8, forward=true, count=0, dest=0x1e097d8) at pquery.c:929
#23 0x0000000000924969 in PortalRun (portal=0x1cf87d8, count=9223372036854775807, isTopLevel=true, run_once=true, dest=0x1e097d8, altdest=0x1e097d8,
completionTag=0x7ffeb0978690 "") at pquery.c:770
#24 0x000000000091e5b4 in exec_simple_query (
query_string=0x1c1fae8 "(((\n SELECT q1 FROM int8_tbl\n INTERSECT\n SELECT q2 FROM int8_tbl ORDER BY 1\n)))\nUNION ALL\nSELECT q2 FROM int8_tbl;")
at postgres.c:1215
#25 0x0000000000922a7c in PostgresMain (argc=1, argv=0x1cb9578, dbname=0x1cb93b8 "postgres", username=0x1cb9390 "postgres") at postgres.c:4247
#26 0x00000000008713bd in BackendRun (port=0x1c3b9f0) at postmaster.c:4448
#27 0x0000000000870b06 in BackendStartup (port=0x1c3b9f0) at postmaster.c:4139
#28 0x000000000086cc46 in ServerLoop () at postmaster.c:1704
#29 0x000000000086c46d in PostmasterMain (argc=3, argv=0x1c1a760) at postmaster.c:1377
#30 0x00000000007850f7 in main (argc=3, argv=0x1c1a760) at main.c:228
```

And if we disable assertions, we get no errors nor warnings.