Fixed production bug where visiting the edit page for a device with no
SNMP discovery data would crash with "expected boolean on left-side of
'and', got: nil" error.
The mikrotik_device?/1 function was using && operator which returns nil
when device.snmp_device is nil, instead of returning false. The template
conditional on line 455 requires a proper boolean value.
Changed from:
device.snmp_device && (...)
To:
not is_nil(device.snmp_device) and (...)
This ensures the function always returns a boolean (true/false) instead
of potentially returning nil.
Added regression test to verify the page renders correctly when a device
has no SNMP discovery data yet.
Fixes: https://app.honeybadger.io/projects/136860/faults/127120431
