Scrolling through streams causes Homebridge to terminate
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# Bug Report

### Describe the Bug
<!-- ✍️edit: --> When scrolling though multiple cameras, e.g., in ATV Control Center, if a stream starts after it's no longer required, a SIGTERM is generated for Homebridge. At this point cameras are unavailable and show a broken stream icon while Homebridge restarts.
Methodically going to each camera works fine, but scrolling quickly past other cameras, e.g., four cameras in this case, causes the error. 

### To Reproduce
Steps to reproduce the behavior:
 - Open Control Center on ATV (long press TV button)
 - Open Home icon
 - Scroll sideways past multiple cameras.

### Expected behavior
<!-- ✍️edit: --> Cameras appear normal, and their streams can be viewed either in preview or full screen.

### Screenshots/Logs
<!-- ✍️edit: --> Homebridge log:
```
[1/29/2021, 4:06:47 PM] [Ring] Preparing Live Stream for Deck
[1/29/2021, 4:06:48 PM] [Ring] Waiting for stream data from Deck (1.092s)
[1/29/2021, 4:06:49 PM] [Ring] Received stream data from Deck (1.545s)
[1/29/2021, 4:06:49 PM] [Ring] Streaming active for Deck
[1/29/2021, 4:06:49 PM] [Ring] Stopped Live Stream for Deck
[1/29/2021, 4:06:49 PM] [Ring] Preparing Live Stream for Driveway
[1/29/2021, 4:06:50 PM] [Ring] Waiting for stream data from Driveway (1.078s)
[1/29/2021, 4:06:50 PM] [Ring] Received stream data from Driveway (1.29s)
[1/29/2021, 4:06:50 PM] [Ring] Streaming active for Driveway
[1/29/2021, 4:06:50 PM] [Ring] Stopped Live Stream for Driveway
Error: SIP request made after call was destroyed
    at SipCall.request (/usr/lib/node_modules/homebridge-ring/lib/api/sip-call.js:117:35)
    at SipCall.sendKeyFrameRequest (/usr/lib/node_modules/homebridge-ring/lib/api/sip-call.js:188:21)
    at SipCall.<anonymous> (/usr/lib/node_modules/homebridge-ring/lib/api/sip-call.js:216:24)
    at Generator.next (<anonymous>)
    at fulfilled (/usr/lib/node_modules/homebridge-ring/lib/api/sip-call.js:5:58)
Error: SIP request made after call was destroyed
    at SipCall.request (/usr/lib/node_modules/homebridge-ring/lib/api/sip-call.js:117:35)
    at SipCall.sendKeyFrameRequest (/usr/lib/node_modules/homebridge-ring/lib/api/sip-call.js:188:21)
    at SipCall.<anonymous> (/usr/lib/node_modules/homebridge-ring/lib/api/sip-call.js:216:24)
    at Generator.next (<anonymous>)
    at fulfilled (/usr/lib/node_modules/homebridge-ring/lib/api/sip-call.js:5:58)
[1/29/2021, 4:06:51 PM] Got SIGTERM, shutting down Homebridge...
Error: SIP request made after call was destroyed
    at SipCall.request (/usr/lib/node_modules/homebridge-ring/lib/api/sip-call.js:117:35)
    at SipCall.sendKeyFrameRequest (/usr/lib/node_modules/homebridge-ring/lib/api/sip-call.js:188:21)
    at SipCall.<anonymous> (/usr/lib/node_modules/homebridge-ring/lib/api/sip-call.js:216:24)
    at Generator.next (<anonymous>)
    at fulfilled (/usr/lib/node_modules/homebridge-ring/lib/api/sip-call.js:5:58)
Error: SIP request made after call was destroyed
    at SipCall.request (/usr/lib/node_modules/homebridge-ring/lib/api/sip-call.js:117:35)
    at SipCall.sendKeyFrameRequest (/usr/lib/node_modules/homebridge-ring/lib/api/sip-call.js:188:21)
    at SipCall.<anonymous> (/usr/lib/node_modules/homebridge-ring/lib/api/sip-call.js:216:24)
    at Generator.next (<anonymous>)
    at fulfilled (/usr/lib/node_modules/homebridge-ring/lib/api/sip-call.js:5:58)
[1/29/2021, 4:06:56 PM] [HB Supervisor] Homebridge Process Ended. Code: 143, Signal: null
[1/29/2021, 4:07:01 PM] [HB Supervisor] Restarting Homebridge...
```

### Additional context
<!-- ✍️edit: --> N/A

### Homebridge Ring Config
```
        {
            "refreshToken": "......",
            "sendCameraMotionNotificationsToTv": true,
            "sendDoorbellMotionNotificationsToTv": false,
            "platform": "Ring"
        },
```

### Environment
<!-- ✍️edit: -->
 - Ring plugin: v9.14.1
 - OS: Ubuntu 19.10 / eoan
 - Node.js: v12.18.3
 - NPM: 6.14.6
 - homebridge:1.2.5
 - hoobs: N/A