# Export/import demo: JSON file event forwarding fix

## Symptom

Selecting a JSON file from the mixed 2D/3D demo failed immediately with:

```text
Cannot read properties of undefined (reading 'target')
```

The state import API was not reached.

## Cause

The shared `withUiError()` event wrapper returned a zero-argument function. Native DOM events passed by `addEventListener()` were therefore discarded before the wrapped handler ran. The JSON input handler expected the original `change` event and tried to read `event.target.files`.

## Fix

The wrapper now forwards every argument received from the DOM:

```js
const withUiError = (action) => async (...args) => {
  try {
    await action(...args);
  } catch (error) {
    // Existing UI error reporting.
  }
};
```

This preserves click handlers while allowing file, input, and future event-driven handlers to receive their native event objects.