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

**To Reproduce**
```sql
SELECT CASE WHEN ( SELECT 2 WHERE FALSE ) > ANY ( 1 ) THEN 1 END GROUP BY 1;
```

**Backtrace of the Crash**
```c
#0 0x7fde17972420 (get_rel_count+0x30)
#1 0x7fde179971e7 (rel_propagate_statistics+0x1327)
#2 0x7fde17969a65 (exp_visitor+0xc45)
#3 0x7fde179685e9 (exps_exp_visitor_bottomup+0xf9)
#4 0x7fde17991ca1 (rel_get_statistics_+0x351)
#5 0x7fde17967de7 (rel_visitor_bottomup+0x3e7)
#6 0x7fde17967c78 (rel_visitor_bottomup+0x278)
#7 0x7fde17967cd7 (rel_visitor_bottomup+0x2d7)
#8 0x7fde179917bf (rel_get_statistics+0x5f)
#9 0x7fde1798e235 (rel_optimizer+0x935)
#10 0x7fde178f04a7 (sql_processrelation+0xc7)
#11 0x7fde176f8edb (sql_symbol2relation+0x1bb)
#12 0x7fde17725a82 (SQLparser+0x802)
#13 0x7fde17724a0a (SQLengine_+0xa5a)
#14 0x7fde177221fe (SQLengine+0x3e)
#15 0x7fde17ca6b2f (runScenario+0x6f)
#16 0x7fde17ca7cfe (MSscheduleClient+0xb6e)
#17 0x7fde17deb6c2 (doChallenge+0x132)
#18 0x7fde18c08b38 (thread_starter+0x318)
#19 0x7fde17619609 (start_thread+0xd9)
#20 0x7fde1753c353 (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 `get_rel_count`
This is a GitHub Issue
repo:MonetDB
owner:MonetDB
Title : MonetDB server crashes in `get_rel_count`
Issue date:

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

**To Reproduce**
```sql
SELECT CASE WHEN ( SELECT 2 WHERE FALSE ) > ANY ( 1 ) THEN 1 END GROUP BY 1;
```

**Backtrace of the Crash**
```c
#0 0x7fde17972420 (get_rel_count+0x30)
#1 0x7fde179971e7 (rel_propagate_statistics+0x1327)
#2 0x7fde17969a65 (exp_visitor+0xc45)
#3 0x7fde179685e9 (exps_exp_visitor_bottomup+0xf9)
#4 0x7fde17991ca1 (rel_get_statistics_+0x351)
#5 0x7fde17967de7 (rel_visitor_bottomup+0x3e7)
#6 0x7fde17967c78 (rel_visitor_bottomup+0x278)
#7 0x7fde17967cd7 (rel_visitor_bottomup+0x2d7)
#8 0x7fde179917bf (rel_get_statistics+0x5f)
#9 0x7fde1798e235 (rel_optimizer+0x935)
#10 0x7fde178f04a7 (sql_processrelation+0xc7)
#11 0x7fde176f8edb (sql_symbol2relation+0x1bb)
#12 0x7fde17725a82 (SQLparser+0x802)
#13 0x7fde17724a0a (SQLengine_+0xa5a)
#14 0x7fde177221fe (SQLengine+0x3e)
#15 0x7fde17ca6b2f (runScenario+0x6f)
#16 0x7fde17ca7cfe (MSscheduleClient+0xb6e)
#17 0x7fde17deb6c2 (doChallenge+0x132)
#18 0x7fde18c08b38 (thread_starter+0x318)
#19 0x7fde17619609 (start_thread+0xd9)
#20 0x7fde1753c353 (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 ---

A crash in the MonetDB server occurs in the `get_rel_count` function when executing a specific SQL query that involves a CASE statement with a subquery that always evaluates to false. This leads to a segmentation fault, indicating a potential vulnerability that could be exploited to cause a Denial of Service (DoS).