If you press [Ctrl]+[C], you will get something like this:

```
meterpreter > webcam_stream
[*] Starting...
[*] Preparing player...
[*] Opening player at: LdvYdvSq.html
[*] Streaming...
^C[-] Error running command webcam_stream: Interrupt 
meterpreter >
```

After that exception, the ensure clause should kick in and then properly shut down the webcam.