Homebridge crashes when viewing Unifi camera
After closing/restarting Homekit app on iPhone, the camera displays the snapshot refresh correctly on the "Home" favourites page, and updates as expected.
However, when the camera snapshot image is clicked, to view the camera feed, Homebridge v 1.1.7 crashes and restarts with this error:

[1/2/2021, 11:32:33 AM] Error: Command failed with ENOENT: ffmpeg -codecs
spawn ffmpeg ENOENT
    at Process.ChildProcess._handle.onexit (node:internal/child_process:276:19)
    at onErrorNT (node:internal/child_process:476:16)
    at processTicksAndRejections (node:internal/process/task_queues:80:21)

Problem started after upgrading homebridge-unifi-protect to v 4.3.0 (and upgrading to Unifi OS to v 2.0.24 as required by homebridge-unifi-protect).  
Problem continues with latest homebridge-unifi-protect v 4.3.5 (released today).

**Versions affected:**
Homebridge v 1.1.7
homebridge-unifi-protect v 4.3.0 and v 4.3.5
Unifi Protect v 1.6.9
Unifi OS v 2.0.24
Node.js v 15.4.0
