"Unused filter" shows incorrect results if "AssetUsage" package is not installed

[Sebobo]

Description

This bug came out of the issue described in #158 in which the AssetUsage package is not used, but the usages feature is enabled.

Steps to Reproduce

1. Turn on usages feature
2. Make sure AssetUsage package is not installed

Expected behavior

The unused filter should only be active if it can actually return proper results

Actual behavior

The unused filter would show assets which are in use

Affected Versions

Media Module: Since usages were integrated

[Sebobo]

Cannot reproduce as the Media UI would throw exceptions if the package is not installed and the filter is being used

[Sebobo]

Hi @peterrauber, if you can somehow reproduce this bug, feel free to reopen or ping me.