fix(ui): gracefully handle deletions in collection with upload hasMany

[akhrarovsaid]

What?

This PR aims to prevent a runtime error by allowing deletions in media collections and preventing them from impacting workflows while using hasMany upload fields.

Why?

To prevent runtime issues during common tasks.

How?

By treating deleted media documents as empty placeholders instead of undefined objects.

Fixes #9328

Before:
Dashboard-before--Payload.webm

After:
Dashboard-after--Payload.webm

Notes:

• There is room for improvement here: allow selection of existing media in upload collection instead of forcing user to upload new. Workaround is to remove the row and choose existing as usual.
• New uploads chosen will always replace the first instance of undefined placeholder due to the simple check. If you have 3 deleted entries and open the drawer on the second one, then it will populate the first one anyway. This can be improved but will require more laborious code changes.
• Noticed an issue where deleted non-hasMany upload fields do not re-render after a file is uploaded. It only shows the previous deleted doc, ie id: "untitled - ID: ...". Re-renders correctly when choosing from existing. This is unrelated to this PR. I will investigate further.
• I'm realizing this actually diverges from what db-postgres does, as deleted entries in a hasMany upload gets removed from the field in the initial deletion probably due to cascading the deletion...