PR: Linked model export fails with non-recoverable error if main model contains pset schedules

### Problem Description

## Problem
When trying to export a linked model and the main model to the same IFC, the export fails if Pset schedules are being used in the main model. Revit will show two errors (loosely translated):
- Unexpected errors when exporting these elements to the IFC file
- A non-recoverable error has occurred during export. Try using filters and the Current view only mode, or look in the documentation for further suggestions. The export is now canceled.

## Steps to reproduce
(Sample models here: https://github.com/andydandy74/MyIssues/tree/master/RevitIFC882)
- Open the main model and make sure the linked model is loaded
- In IFC export dialogue choose "Export to same Site" for the link export behaviour and start the export
- Observe that an IFC model is created
- Bring up the IFC dialogue again, check the two checkboxes for Pset schedules and try exporting again
- No model exported, warning/error messages instead

### Revit Version

2025.4.x

### IFC for Revit Addon Version

25.4.0

### Windows Version

11 24H2

Start with the RevitIFC882 sample models and reproduce the export on Revit 2025.4.x with IFC for Revit 25.4.0. Compare exporting the linked and main models with and without the two Pset schedule checkboxes enabled. Done means the same-Site export completes and produces an IFC without the reported errors.

Written by the indexing model from the issue text.