empty Fan object results in panic/crash

An empty Fan object was created which then crashed the hkknx process. Upon restart, the configuration is loaded but causes an immediate crash of hkknx. Process is unable to be restarted successfully until invalid accessory is removed from database/server.json. Stack trace below.

Version 2.0.1

Steps to reproduce:

backup the configuration - cp server.json server.json.ok
add new Fan object and click Save - do not change any fields
crash

Seems likely that the non-optional attribute rotation-speed is missing a validation check before the object is created.

~/database $ cat server.json.ok | jq '.' > a
~/database $ cat server.json.crash | jq '.' > b
~/database $ diff a b
56468a56469,56502
>     },
>     {
>       "id": "840e72ee-0316-4ae7-adff-71b7e8d72637",
>       "pid": "1660eedd-2f09-42a8-b2d7-7505d29c1bb4",
>       "name": "Fan",
>       "manufacturer": "",
>       "model": "",
>       "room": "",
>       "archived": false,
>       "disabled": false,
>       "created_at": "2021-11-02T14:44:34.885496775+02:00",
>       "service": {
>         "type": "fan",
>         "properties": [
>           {
>             "type": "rotation-speed",
>             "dpst": "DPST-5-1",
>             "listen": "",
>             "write": "",
>             "init": "",
>             "optional": false,
>             "enabled": false
>           },
>           {
>             "type": "block",
>             "dpst": "DPT-1",
>             "listen": "",
>             "write": "",
>             "init": "",
>             "optional": true,
>             "enabled": false
>           }
>         ]
>       }

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x4 pc=0x623c6c]

goroutine 98 [running]:
github.com/brutella/hkknx/app.(*Fan).bind(0x1711c60, 0x1711c40, 0xaf969c, 0x1480558)
    /Users/mah/Source/Code/Go/src/github.com/brutella/hkknx/app/fan.go:23 +0x78
github.com/brutella/hkknx/app.(*app).accessoriesInProject(0x1146500, 0x111dc80, 0xaf969c, 0x1480558, 0xea5de0, 0x1, 0x0, 0x0)
    /Users/mah/Source/Code/Go/src/github.com/brutella/hkknx/app/app.go:952 +0x364
github.com/brutella/hkknx/app.(*app).Run.func2(0xaf582c, 0x100a8a0, 0x111dc80, 0x1146500, 0x1480558, 0x1026d70)
    /Users/mah/Source/Code/Go/src/github.com/brutella/hkknx/app/app.go:353 +0x144
created by github.com/brutella/hkknx/app.(*app).Run
    /Users/mah/Source/Code/Go/src/github.com/brutella/hkknx/app/app.go:344 +0x434

brutella / hkknx-public

empty Fan object results in panic/crash #145