Please add error handler in api\ffmpeg.js to prevent uncatchable exceptions
# Bug Report

### Describe the Bug
We use your library in one of our ioBroker adapter and we see several uncatchable crashes:

Error [ERR_STREAM_DESTROYED] doWrite(_stream_writable): 



... in this case there seems to be cases where a call to "start" on ffmpeg on a closed stdin. I think it would be an idea to add error handlers on stdin.

We use 8.x version here, but I checked and that code part was basically not changed in later versions.

### To Reproduce
I can not tell you that, we just See the crashes in our sentry. We see 70 affected users (from 700 having the adapter installed)

### Expected behavior

it do not crashes. This means the exception is somehow catchable by our code or catched by library code

### Screenshots/Logs
Details see: https://sentry.iobroker.net/share/issue/7e22d3b15cc446d49b2da387c1846f6a/ 

```
Error: Cannot call write after a stream was destroyed
  File "_stream_writable.js", line 399, col 19, in doWrite
  File "_stream_writable.js", line 387, col 5, in writeOrBuffer
  File "_stream_writable.js", line 318, col 11, in Socket.Writable.write
  File "/opt/iobroker/node_modules/ring-client-api/lib/api/ffmpeg.js", line 76, col 23, in FfmpegProcess.start
    this.ff.stdin.write(input);
  File "/opt/iobroker/node_modules/ring-client-api/lib/api/sip-session.js", line 125, col 16, in SipSession.<anonymous>
    ff.start(inputSdpLines.filter((x) => Boolean(x)).join('\n'));
  ?, in Generator.next
  File "/opt/iobroker/node_modules/ring-client-api/lib/api/sip-session.js", line 5, col 58, in fulfilled
    function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
  File "internal/process/task_queues.js", line 97, col 5, in processTicksAndRejections
```

### Additional context


### Environment
<!-- ✍️edit: -->
 - OS: Linux based and also Windows!
 - Node.js: mostly 12.8.x
 - NPM: unknown
 - ring-client-api: 8.2.0
