Not able to approve renewals

One-sentence description

The 'approve' button on the renewals page is dead

Current behaviour

When hitting the 'approve' button, nothing happens and the page deadlocks. When doing it from the renewals overview (selecting and action via the dropdown menu) everything works fine luckily.

Expected behaviour

A working button the renewal.

Steps to reproduce

1. Look for an open renewal that needs approval.
2. Try to approve it by hitting the green button
3. Profit!