RTREE index is not used

### What happens?

If I create a table with a geometry column and an id column RTREE index is not used:
When, if I create the table with only the geometry column, then the RTREE index is used.

### To Reproduce

```
INSTALL spatial;
LOAD spatial;

CREATE TABLE IF NOT EXISTS t1 (
id LONG PRIMARY KEY,
geom GEOMETRY
);

-- Create a table with 10_000_000 random points
INSERT INTO t1(id, geom)
SELECT row_number() OVER (), point
FROM st_generatepoints({min_x: 0, min_y: 0, max_x: 100, max_y: 100}::BOX_2D, 10_000, 1337);

-- Create an index on the table.
CREATE INDEX my_idx ON t1 USING RTREE (geom);

-- Perform a query with a "spatial predicate" on the indexed geometry column
-- Note how the second argument in this case, the ST_MakeEnvelope call is a "constant"
SELECT count(*) FROM t1 WHERE ST_Within(geom, ST_MakeEnvelope(45, 45, 65, 65));

-- RTREE is not used
EXPLAIN SELECT count(*) FROM t1 WHERE ST_Within(geom, ST_MakeEnvelope(45, 45, 65, 65));
```

### OS:

MacOS

### DuckDB Version:

1.5

### DuckDB Client:

CLI

### Hardware:

_No response_

### Full Name:

Maurizio Merli

### Affiliation:

Xthema

### Did you include all relevant configuration (e.g., CPU architecture, Linux distribution) to reproduce the issue?

- [x] Yes, I have

### Did you include all code required to reproduce the issue?

- [x] Yes, I have

### Did you include all relevant data sets for reproducing the issue?

Yes