The hourly AMS sensor recorder dispatched humidity and temperature alarms
for every unit above threshold without checking whether the unit was
actually loaded. Empty AMS units still report ambient readings, so users
with one loaded + one empty AMS got useful alarms for the loaded one and
hourly noise for the empty one. Disabling the whole alarm category killed
both — not a real choice.
New _ams_has_filament helper inspects tray_exist_bits (hex bitmap, "0" =
empty) with fallback to the tray array's tray_type strings for shapes
where the bitmap is missing. The recorder gates the alarm dispatch on
this check per-AMS-unit, so a multi-AMS printer with one loaded + one
empty still alarms on the loaded one.
Sensor history still records regardless of the gate so the System page
humidity charts stay continuous — only the outbound notification is
suppressed. 9 unit tests cover the bitmap-zero case, bitmap-missing
fallback, garbage/blank/int bitmap edges, and defensive malformed tray.