[Bug] Again. Shelly Bulbs do let the HOOBS server crash
**Describe the bug**
I am switching the bulbs with a shelly 2.5. They are configured to go on if power (from shelly 2.5) is on. Service crashes immediately after. If I remove the bulbs from the admin console, it runs ok, till (sorry haven't thought about this before) I restart HOOBS. After that everything crashes as before. Worked ok with firmware <0.15.0

**Log output**
6.9.2020, 18:19:16 TypeError: Cannot read property 'type' of null
    at Immediate.<anonymous> (/home/hoobs/.hoobs/node_modules/homebridge-shelly/abilities/color-lightbulb.js:184:23)
    at processImmediate (internal/timers.js:456:21)
6.9.2020, 18:19:16 TypeError: Cannot read property 'type' of null
    at Immediate.<anonymous> (/home/hoobs/.hoobs/node_modules/homebridge-shelly/abilities/color-lightbulb.js:184:23)
    at processImmediate (internal/timers.js:456:21)
6.9.2020, 18:19:16 Got SIGTERM, shutting down Bridge...
6.9.2020, 18:19:17 HAP Warning: Characteristic 00000093-0000-1000-8000-0026BB765291 not in required or optional characteristics for service 0000008D-0000-1000-8000-0026BB765291. Adding anyway.
6.9.2020, 18:19:17 [eveatmo platform] Initializing platform accessory "Fagusweg 11 Wetterstation"...
6.9.2020, 18:19:17 Bridge is running on port 51826.

**Environment:**
 - Shelly device(s): [e.g. Shelly 2.5] Shelly bulb
 - Plugin version: [e.g. 0.14.0] 0.15.3
 - Device running homebridge: [e.g. Raspberry Pi] Raspberry Pi
Thanks in advance Peter Jäger.
