Optimizer extensions do not have access to query

Hello,

after a solid couple of hours spent on debugging, I came to a conclusion that unfortunately behavior I encountered is a bug somewhere in DuckDB (my guess is duckdb-java, but it might as well be somewhere else).

I'm currently writing an extension, in which I wanted to capture user's queries. It worked just fine in DuckDB CLI, but when I loaded it into the JDBC version of DuckDB, it threw some nasty exceptions:

```
INTERNAL Error: Attempted to dereference unique_ptr that is NULL!

Stack Trace:

/home/miosp/.duckdb/extensions/v1.4.3/linux_amd64/my-extension.duckdb_extension(+0x782414) [0x7f004ccde414]
/home/miosp/.duckdb/extensions/v1.4.3/linux_amd64/my-extension.duckdb_extension(+0x7824bf) [0x7f004ccde4bf]
/home/miosp/.duckdb/extensions/v1.4.3/linux_amd64/my-extension.duckdb_extension(+0x784a71) [0x7f004cce0a71]
/home/miosp/.duckdb/extensions/v1.4.3/linux_amd64/my-extension.duckdb_extension(+0x20083a) [0x7f004c75c83a]
/home/miosp/.duckdb/extensions/v1.4.3/linux_amd64/my-extension.duckdb_extension(+0x47bc7f) [0x7f004c9d7c7f]
/tmp/libduckdb_java9599730312245461022.so(+0x128e924) [0x7f007a33b924]
/tmp/libduckdb_java9599730312245461022.so(+0x128ea5c) [0x7f007a33ba5c]
/tmp/libduckdb_java9599730312245461022.so(+0x1290674) [0x7f007a33d674]
/tmp/libduckdb_java9599730312245461022.so(+0x118488f) [0x7f007a23188f]
/tmp/libduckdb_java9599730312245461022.so(+0x1184ba1) [0x7f007a231ba1]
/tmp/libduckdb_java9599730312245461022.so(+0x1184fac) [0x7f007a231fac]
/tmp/libduckdb_java9599730312245461022.so(+0x1167ffc) [0x7f007a214ffc]
/tmp/libduckdb_java9599730312245461022.so(+0x11681ed) [0x7f007a2151ed]
/tmp/libduckdb_java9599730312245461022.so(+0x118e2c5) [0x7f007a23b2c5]
/tmp/libduckdb_java9599730312245461022.so(+0x118e36b) [0x7f007a23b36b]
/tmp/libduckdb_java9599730312245461022.so(+0x509315) [0x7f00795b6315]
/tmp/libduckdb_java9599730312245461022.so(Java_org_duckdb_DuckDBNative_duckdb_1jdbc_1prepare+0x11) [0x7f00795ba141]
[0x7f02e626eb6d]
```

I tried to dig into the issue and i developed a minimal PoC of the issue (strapped onto the extension template repository and switched both DuckDB and CI tools versions to 1.4.3 to be sure).

Then, I modified the `quack_extension.cpp` to:

```cpp
#define DUCKDB_EXTENSION_MAIN

#include "quack_extension.hpp"
#include "duckdb.hpp"
#include "duckdb/common/exception.hpp"
#include "duckdb/function/scalar_function.hpp"
#include

namespace duckdb {

void PreOptimize(OptimizerExtensionInput &input, unique_ptr &plan) {
if (!plan) {
return;
}

string query;
try {
query = input.context.GetCurrentQuery();
} catch (...) {
Printer::Print("Caught some Exception");
return;
}

Printer::Print("QuackExtension PreOptimize called for query: " + query);

return;
}

static void LoadInternal(ExtensionLoader &loader) {
auto &db_instance = loader.GetDatabaseInstance();
auto &config = db_instance.config;

OptimizerExtension extension;
extension.pre_optimize_function = &PreOptimize;

config.optimizer_extensions.push_back(extension);
}

void QuackExtension::Load(ExtensionLoader &loader) {
LoadInternal(loader);
}
std::string QuackExtension::Name() {
return "quack";
}

std::string QuackExtension::Version() const {
#ifdef EXT_VERSION_QUACK
return EXT_VERSION_QUACK;
#else
return "";
#endif
}

} // namespace duckdb

extern "C" {

DUCKDB_CPP_EXTENSION_ENTRY(quack, loader) {
duckdb::LoadInternal(loader);
}
}
```

When i launch the extension from the CLI i get:
```
duckdb -unsigned
DuckDB v1.4.3 (Andium) d1dc88f950
Enter ".help" for usage hints.
D LOAD '/home/miosp/proj/extension-template/build/release/repository/v1.4.3/linux_amd64/quack.duckdb_extension';
D pragma VERSION;
QuackExtension PreOptimize called for query: SELECT * FROM pragma_version();
┌─────────────────┬────────────┬──────────┐
│ library_version │ source_id │ codename │
│ varchar │ varchar │ varchar │
├─────────────────┼────────────┼──────────┤
│ v1.4.3 │ d1dc88f950 │ Andium │
└─────────────────┴────────────┴──────────┘
```

But through the Java JDBC driver I get (after issuing the same commands programatically):
```
Caught some Exception
```

So the output is still correct, but the query was not attached to the context.

I also noticed that if I connect DuckLake to my JDBC DuckDB, the auxiliary queries are caught correctly (I believe this one is for `SHOW ALL TABLES;`):
```
QuackExtension PreOptimize called for query: BEGIN TRANSACTION
QuackExtension PreOptimize called for query:
SELECT * FROM postgres_query('__ducklake_metadata_miosp_ducklake',
'SELECT snapshot_id, schema_version, next_catalog_id, next_file_id
FROM "public".ducklake_snapshot WHERE snapshot_id = (
SELECT MAX(snapshot_id) FROM "public".ducklake_snapshot
);')

QuackExtension PreOptimize called for query: COMMIT
QuackExtension PreOptimize called for query: BEGIN TRANSACTION
QuackExtension PreOptimize called for query:
SELECT * FROM postgres_query('__ducklake_metadata_miosp_ducklake',
'SELECT snapshot_id, schema_version, next_catalog_id, next_file_id
FROM "public".ducklake_snapshot WHERE snapshot_id = (
SELECT MAX(snapshot_id) FROM "public".ducklake_snapshot
);')

Caught some Exception
QuackExtension PreOptimize called for query: COMMIT
Caught some Exception
Caught some Exception
QuackExtension PreOptimize called for query: BEGIN TRANSACTION
QuackExtension PreOptimize called for query:
SELECT * FROM postgres_query('__ducklake_metadata_miosp_ducklake',
'SELECT snapshot_id, schema_version, next_catalog_id, next_file_id
FROM "public".ducklake_snapshot WHERE snapshot_id = (
SELECT MAX(snapshot_id) FROM "public".ducklake_snapshot
);')

QuackExtension PreOptimize called for query: COMMIT
Caught some Exception
```

Am I doing something wrong, or this is a legitimate bug?