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

**To Reproduce**
```sql
SELECT ( WITH x AS ( SELECT 1 x UNION SELECT 1 ) SELECT x FROM x WHERE ( SELECT x FROM ( SELECT ( CASE WHEN 1 THEN x END ) x , 1 * x FROM x UNION SELECT x , x ) AS ) );
```

**Backtrace of the Crash**
```c
#0 0x7fa5ab1eee3c (rel_optimize_projections_+0xb0c)
#1 0x7fa5ab19c33f (rel_visitor_topdown+0x27f)
#2 0x7fa5ab19c6f5 (rel_visitor_topdown+0x635)
#3 0x7fa5ab19c696 (rel_visitor_topdown+0x5d6)
#4 0x7fa5ab19c6f5 (rel_visitor_topdown+0x635)
#5 0x7fa5ab19c658 (rel_visitor_topdown+0x598)
#6 0x7fa5ab19c6f5 (rel_visitor_topdown+0x635)
#7 0x7fa5ab19c696 (rel_visitor_topdown+0x5d6)
#8 0x7fa5ab19c6f5 (rel_visitor_topdown+0x635)
#9 0x7fa5ab19c6f5 (rel_visitor_topdown+0x635)
#10 0x7fa5ab19c6f5 (rel_visitor_topdown+0x635)
#11 0x7fa5ab19c696 (rel_visitor_topdown+0x5d6)
#12 0x7fa5ab19c6f5 (rel_visitor_topdown+0x635)
#13 0x7fa5ab1e8c4b (rel_optimize_projections+0x3b)
#14 0x7fa5ab1c305a (rel_optimizer+0x75a)
#15 0x7fa5ab1254a7 (sql_processrelation+0xc7)
#16 0x7fa5aaf2dedb (sql_symbol2relation+0x1bb)
#17 0x7fa5aaf5aa82 (SQLparser+0x802)
#18 0x7fa5aaf59a0a (SQLengine_+0xa5a)
#19 0x7fa5aaf571fe (SQLengine+0x3e)
#20 0x7fa5ab4dbb2f (runScenario+0x6f)
#21 0x7fa5ab4dccfe (MSscheduleClient+0xb6e)
#22 0x7fa5ab6206c2 (doChallenge+0x132)
#23 0x7fa5ac43db38 (thread_starter+0x318)
#24 0x7fa5aae4e609 (start_thread+0xd9)
#25 0x7fa5aad71353 (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_optimize_projections_`
This is a GitHub Issue
repo:MonetDB
owner:MonetDB
Title : MonetDB server crashes in `rel_optimize_projections_`
Issue date:

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

**To Reproduce**
```sql
SELECT ( WITH x AS ( SELECT 1 x UNION SELECT 1 ) SELECT x FROM x WHERE ( SELECT x FROM ( SELECT ( CASE WHEN 1 THEN x END ) x , 1 * x FROM x UNION SELECT x , x ) AS ) );
```

**Backtrace of the Crash**
```c
#0 0x7fa5ab1eee3c (rel_optimize_projections_+0xb0c)
#1 0x7fa5ab19c33f (rel_visitor_topdown+0x27f)
#2 0x7fa5ab19c6f5 (rel_visitor_topdown+0x635)
#3 0x7fa5ab19c696 (rel_visitor_topdown+0x5d6)
#4 0x7fa5ab19c6f5 (rel_visitor_topdown+0x635)
#5 0x7fa5ab19c658 (rel_visitor_topdown+0x598)
#6 0x7fa5ab19c6f5 (rel_visitor_topdown+0x635)
#7 0x7fa5ab19c696 (rel_visitor_topdown+0x5d6)
#8 0x7fa5ab19c6f5 (rel_visitor_topdown+0x635)
#9 0x7fa5ab19c6f5 (rel_visitor_topdown+0x635)
#10 0x7fa5ab19c6f5 (rel_visitor_topdown+0x635)
#11 0x7fa5ab19c696 (rel_visitor_topdown+0x5d6)
#12 0x7fa5ab19c6f5 (rel_visitor_topdown+0x635)
#13 0x7fa5ab1e8c4b (rel_optimize_projections+0x3b)
#14 0x7fa5ab1c305a (rel_optimizer+0x75a)
#15 0x7fa5ab1254a7 (sql_processrelation+0xc7)
#16 0x7fa5aaf2dedb (sql_symbol2relation+0x1bb)
#17 0x7fa5aaf5aa82 (SQLparser+0x802)
#18 0x7fa5aaf59a0a (SQLengine_+0xa5a)
#19 0x7fa5aaf571fe (SQLengine+0x3e)
#20 0x7fa5ab4dbb2f (runScenario+0x6f)
#21 0x7fa5ab4dccfe (MSscheduleClient+0xb6e)
#22 0x7fa5ab6206c2 (doChallenge+0x132)
#23 0x7fa5ac43db38 (thread_starter+0x318)
#24 0x7fa5aae4e609 (start_thread+0xd9)
#25 0x7fa5aad71353 (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 `rel_optimize_projections_` function when executing a complex SQL query. This issue can lead to a Denial of Service (DoS) as the server becomes unresponsive and crashes when processing specific SQL statements. The backtrace indicates that the crash is likely due to infinite recursion or stack overflow during the optimization of projections in the query.