Exported packed arrays constructed from arrays are null in the inspector

### Tested versions

4.5 dev4

### System information

W10

### Issue description

If you export a packed array property like this:
```GDScript
@export var weights := PackedFloat32Array([5.25, 4.25, 3, 2, 1.5])
```
It's null in the inspector


When you click it, there are no elements and you can revert it back to null.

This works correctly:
```GDScript
@export var weights: PackedFloat32Array = [5.25, 4.25, 3, 2, 1.5]
```

### Steps to reproduce

See above.

### Minimal reproduction project (MRP)

N/A