**Describe the bug**
MonetDB server crashes in `rel_get_statistics_`.

**To Reproduce**
```sql
SELECT NTILE ( 1.000000 ) OVER ( ORDER BY x LIKE x ) FROM ( SELECT 'x' x UNION SELECT 10 x ) v;
```

**Backtrace of the Crash**
```c
#0 0x7fa5dc469972 (rel_get_statistics_+0x1022)
#1 0x7fa5dc43ede7 (rel_visitor_bottomup+0x3e7)
#2 0x7fa5dc43ecd7 (rel_visitor_bottomup+0x2d7)
#3 0x7fa5dc43ecd7 (rel_visitor_bottomup+0x2d7)
#4 0x7fa5dc43ecd7 (rel_visitor_bottomup+0x2d7)
#5 0x7fa5dc4687bf (rel_get_statistics+0x5f)
#6 0x7fa5dc465235 (rel_optimizer+0x935)
#7 0x7fa5dc3c74a7 (sql_processrelation+0xc7)
#8 0x7fa5dc1cfedb (sql_symbol2relation+0x1bb)
#9 0x7fa5dc1fca82 (SQLparser+0x802)
#10 0x7fa5dc1fba0a (SQLengine_+0xa5a)
#11 0x7fa5dc1f91fe (SQLengine+0x3e)
#12 0x7fa5dc77db2f (runScenario+0x6f)
#13 0x7fa5dc77ecfe (MSscheduleClient+0xb6e)
#14 0x7fa5dc8c26c2 (doChallenge+0x132)
#15 0x7fa5dd6dfb38 (thread_starter+0x318)
#16 0x7fa5dc0f0609 (start_thread+0xd9)
#17 0x7fa5dc013353 (clone+0x43)
```

**Software versions**
 - MonetDB version number: v11.49.1 (Dec2023)
 - OS and version: Ubuntu 20.04
 - From docker image monetdb/monetdb:Dec2023 (or monetdb/dev-builds:default)

An example of steps to reproduce in docker container (**write the poc into /tmp/test.sql first**):
```bash
docker container rm monetdb_test -f
docker run -e MDB_DB_ADMIN_PASS=monetdb --name monetdb_test -itd monetdb/monetdb:Dec2023
docker exec monetdb_test bash -c 'echo -n -e "user=monetdb\npassword=monetdb\n" > /root/.monetdb'

sleep 10
cat /tmp/test.sql | timeout 5s docker exec -i monetdb_test mclient monetdb     # run test case

if docker exec monetdb_test bash -c "grep '[m]server5' /proc/*/cmdline -lR"; then
    echo "[INFO] Server normal."
else
    echo "[CRASH] Mserver5 process does NOT exist."
fi
```

It can also be reproduced on the docker image `monetdb/dev-builds:default`.

**Issue labeling**
bug
MonetDB server crashes in `rel_get_statistics_`
This is a GitHub Issue
repo:MonetDB
owner:MonetDB
Title : MonetDB server crashes in `rel_get_statistics_`
Issue date:

--- start body ---
**Describe the bug**
MonetDB server crashes in `rel_get_statistics_`.

**To Reproduce**
```sql
SELECT NTILE ( 1.000000 ) OVER ( ORDER BY x LIKE x ) FROM ( SELECT 'x' x UNION SELECT 10 x ) v;
```

**Backtrace of the Crash**
```c
#0 0x7fa5dc469972 (rel_get_statistics_+0x1022)
#1 0x7fa5dc43ede7 (rel_visitor_bottomup+0x3e7)
#2 0x7fa5dc43ecd7 (rel_visitor_bottomup+0x2d7)
#3 0x7fa5dc43ecd7 (rel_visitor_bottomup+0x2d7)
#4 0x7fa5dc43ecd7 (rel_visitor_bottomup+0x2d7)
#5 0x7fa5dc4687bf (rel_get_statistics+0x5f)
#6 0x7fa5dc465235 (rel_optimizer+0x935)
#7 0x7fa5dc3c74a7 (sql_processrelation+0xc7)
#8 0x7fa5dc1cfedb (sql_symbol2relation+0x1bb)
#9 0x7fa5dc1fca82 (SQLparser+0x802)
#10 0x7fa5dc1fba0a (SQLengine_+0xa5a)
#11 0x7fa5dc1f91fe (SQLengine+0x3e)
#12 0x7fa5dc77db2f (runScenario+0x6f)
#13 0x7fa5dc77ecfe (MSscheduleClient+0xb6e)
#14 0x7fa5dc8c26c2 (doChallenge+0x132)
#15 0x7fa5dd6dfb38 (thread_starter+0x318)
#16 0x7fa5dc0f0609 (start_thread+0xd9)
#17 0x7fa5dc013353 (clone+0x43)
```

**Software versions**
 - MonetDB version number: v11.49.1 (Dec2023)
 - OS and version: Ubuntu 20.04
 - From docker image monetdb/monetdb:Dec2023 (or monetdb/dev-builds:default)

An example of steps to reproduce in docker container (**write the poc into /tmp/test.sql first**):
```bash
docker container rm monetdb_test -f
docker run -e MDB_DB_ADMIN_PASS=monetdb --name monetdb_test -itd monetdb/monetdb:Dec2023
docker exec monetdb_test bash -c 'echo -n -e "user=monetdb\npassword=monetdb\n" > /root/.monetdb'

sleep 10
cat /tmp/test.sql | timeout 5s docker exec -i monetdb_test mclient monetdb     # run test case

if docker exec monetdb_test bash -c "grep '[m]server5' /proc/*/cmdline -lR"; then
    echo "[INFO] Server normal."
else
    echo "[CRASH] Mserver5 process does NOT exist."
fi
```

It can also be reproduced on the docker image `monetdb/dev-builds:default`.

**Issue labeling**
bug
--- end body ---
