[Bug] Error when hovering over invalid `:nth-child` instruction

[HoferMarkus]

Reproducible in vscode.dev or in VS Code Desktop?

• Not reproducible in vscode.dev or VS Code Desktop

Reproducible in the monaco editor playground?

• Not reproducible in the monaco editor playground

Monaco Editor Playground Link

https://microsoft.github.io/monaco-editor/playground.html?source=v0.55.1#XQAAAAJqAQAAAAAAAABBqQkHQ5NjdMjwa-jY7SIQ9S7DNlzs5W-mwj0fe1ZCDRFc9ws9XQE0SJE1jc2VKxhaLFIw9vEWSxW3yscwzX_uRgmSaumWUF-TBOsVJ4S4FwfCDQb5-2uUHXTVAefbVSd9IzaZ_vv9VR9KugsKimARHSWlrTPOQHROITHxmAfWyxxqJxKmhw1cKTUXC0tx2LpbUNTPmPakHwRDCMzdoAiklOMc0p3Nr1fBa5SNIwkn6xD0gCTG5vcEJD-YrwETkeoWK28F2pb0Xq2fx4k1Ro7TuHxRZ1iSvU7MtPNYGKzp0ebj-RR9nalP9jmhdCOn5j5ER-RZjhXLtDzaRkrurbfokzAEOcnE5RBpV-y-cxtaDh4MvXt4BxzTpLB0fRna43Wbadj-9N5-_A

Monaco Editor Playground Code

:nth-child()

Reproduction Steps

• Create Monaco editor instance with CSS language
• Write an invalid nth-child selector, e.g. just a plain :nth-child()
• Hover over the nth-child text

Actual (Problematic) Behavior

Editor throws with:

TypeError: Cannot read properties of undefined (reading 'getText')
at r (css.worker-HnVq6Ewq.js:50:3825)
at r (css.worker-HnVq6Ewq.js:50:4197)
at Fm.selectorToSpecificityMarkedString (css.worker-HnVq6Ewq.js:50:4254)
at Fm.selectorToMarkedString (css.worker-HnVq6Ewq.js:50:2263)
at ps.doHover (css.worker-HnVq6Ewq.js:50:6293)
at _f.doHover (css.worker-HnVq6Ewq.js:93:10456)
at Rt.$fmr (css.worker-HnVq6Ewq.js:26:15794)
at Gh._handleMessage (css.worker-HnVq6Ewq.js:7:36565)
at Object.handleMessage (css.worker-HnVq6Ewq.js:7:36059)
at Hh._handleRequestMessage (css.worker-HnVq6Ewq.js:7:34816)
at r (css.worker-HnVq6Ewq.js:50:3825)
at r (css.worker-HnVq6Ewq.js:50:4197)
at Fm.selectorToSpecificityMarkedString (css.worker-HnVq6Ewq.js:50:4254)
at Fm.selectorToMarkedString (css.worker-HnVq6Ewq.js:50:2263)
at ps.doHover (css.worker-HnVq6Ewq.js:50:6293)
at _f.doHover (css.worker-HnVq6Ewq.js:93:10456)
at Rt.$fmr (css.worker-HnVq6Ewq.js:26:15794)
at Gh._handleMessage (css.worker-HnVq6Ewq.js:7:36565)
at Object.handleMessage (css.worker-HnVq6Ewq.js:7:36059)
at Hh._handleRequestMessage (css.worker-HnVq6Ewq.js:7:34816)
at editor.api-CalNCsUg.js:3:12

In the PG the error is shown in console.
In my real world application the editor instance actually throws, triggering the app-specific error handling (generic error dialog, etc..)

Expected Behavior

No response

Additional Context

No response