Mentions v1.8.4 not working with flarum core 1.8.5

[SvenLie]

Current Behavior

Cause of issue #4063 i rolled back flarum core to 1.8.5. After that (with activated email notification for mentions) a post throwed an error. With core 1.8.6 its working correct. There is a dependency between mentions 1.8.4 and core 1.8.6 missing.

Steps to Reproduce

1. Install core 1.8.5 and mentions 1.8.4
2. Activate email notification on post mention in settings
3. Try to mention user with activiated notification with another user
4. Error is showing

Expected Behavior

No error and correct dependency between packages

Screenshots

No response

Environment

• Flarum version: 1.8.5

Output of php flarum info

No response

Possible Solution

No response

Additional Context

No response