fix: Delete mutation should not throw error if no objects in filterset

[keithhackbarth]

Description

When running a batched delete mutation, if no objects are in the filter set, the mutation should be no-op, and an empty array should be returned. This matches the behavior of a batched update and also ensures idempotence.

Current behavior: An empty set throws an error
Expected behavior: An empty set does not throw an error

Scope of change:

• Remove a seemingly necessary assert statement.
• Add some tests (including a breaking test)

Types of Changes

• Core
• Bugfix
• New feature
• Enhancement/optimization
• Documentation

Issues Fixed or Closed by This PR

n/a

Checklist

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• I have tested the changes and verified that they work and don't break anything (as well as I can manage).

[sourcery-ai]

Hey @keithhackbarth - I've reviewed your changes and they look great!

Here's what I looked at during the review

• 🟡 General issues: 1 issue found
• 🟢 Security: all looks good
• 🟢 Testing: all looks good
• 🟢 Complexity: all looks good

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[bellini666]

Nice, thank you! :)