Fixes #5430

Summary

With a file open and no folder, Quick Open (Ctrl+P) never showed the palette. QuickOpenCommand.run() lets that state through on purpose (it only gives up when there is neither a folder nor a tab), then lists the open tabs through _getPath(), which read this._folderState.projectTree!.pathname. projectTree is null in that state, so run() rejected with a TypeError and handleShow only logged it.

_getPath() now treats a missing folder like a file outside the folder and returns the full path as title and description, which is what it already did for files outside the opened folder. Nothing changes when a folder is open. _doSearch() already handled the no-folder case on its own, so run() was the only path that failed.

Type of change

• Bug fix (non-breaking, fixes an issue)
• New feature (non-breaking, adds functionality)
• Breaking change (causes existing functionality to change)
• Documentation update

Test plan

• New tests added (or explain why not needed)
• Manually tested on:

packages/desktop/test/unit/specs/quick-open-without-folder.spec.ts calls run() with one open tab (plus an untitled one), first with no folder and then with a folder that contains the file. On develop (73b90a7) the no-folder case fails with promise rejected "TypeError: Cannot read properties of null…" instead of resolving, thrown at quickOpen.ts:216. With the fix both tests pass. The whole desktop unit suite passes (60 files, 820 tests), vue-tsc --noEmit is clean, and eslint reports no errors on the two files. I ran this on Linux under vitest and did not try the shortcut in a built app.

Notes for reviewers [optional]

The same file builds the tab filter RegExp from a SPECIAL_CHARS class that leaves out { and }, like the Find escaping fixed in #5428. I kept that out of this PR.

By submitting this pull request, I confirm that my contribution is made under the terms of the MIT license.

Found by a defect-hunting pipeline I build and run (Dev-next-gen), using Claude Code with Anthropic's Claude Opus 5.