Merge requests filter doesn't work on dashboard if only approvers filter is specified

Summary

Merge requests filter doesn't work on dashboard if only approvers filter is specified

Steps to reproduce

• Go to https://gitlab.com/dashboard/merge_requests page
• Specify only approver filter (for example: approver: victornoel)

What is the current bug behavior?

It displays "Please select at least one filter to see results" message

What is the expected correct behavior?

It returns all the MRs to which the user is assigned