<!-- This is an auto-generated description by cubic. -->
## Summary by cubic
Stop throwing an error when the user cancels folder selection in the
import dialog. The mutation now returns null, so cancelling the picker
doesn’t show an error or disrupt the flow.

<sup>Written for commit 3c2e61bc723a3ff72cc269c31f715b440fc3695b.
Summary will update on new commits.</sup>

<!-- End of auto-generated description by cubic. -->

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> Prevents erroneous failures when the user cancels the folder picker.
> 
> - In `ImportAppDialog`, `selectFolderMutation` now returns `null` when
no `path`/`name` is provided (user canceled) instead of throwing,
avoiding error toasts and treating cancel as a no-op.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
3c2e61bc723a3ff72cc269c31f715b440fc3695b. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->