video-quickstart-ios: Disabling local video track causes crash

I am using TwilioVideo for calls over the internet. I am trying to support disabling video.

Based on the example code, I expected this would do the trick:

localVideoTrack?.isEnabled = false

Where localVideoTrack is an instance of TVILocalVideoTrack created using:

let camera = TVICameraCapturer(source: .frontCamera, delegate: self)
localVideoTrack = TVILocalVideoTrack.init(capturer: camera!)

I used basically the same approach with the TVILocalAudioTrack to mute and unmute microphone, which works like a charm.

However, with video, when I call:

localVideoTrack?.isEnabled = false

I get a crash:

2018-09-25 17:58:47.270895+0200 App[714:101541] -[TVIRTCI420Buffer coreVideoFrameBuffer]: unrecognized selector sent to instance 0x280d8ce00
2018-09-25 17:58:47.289063+0200 App[714:101541] Encountered an uncaught exception. All Mixpanel instances were archived.
2018-09-25 17:58:47.289128+0200 App[714:101541] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[TVIRTCI420Buffer coreVideoFrameBuffer]: unrecognized selector sent to instance 0x280d8ce00'
*** First throw call stack:
(0x18f53bef8 0x18e709a40 0x18f453154 0x18f541810 0x18f5434bc 0x1043b754c 0x1043b6cac 0x1043f4524 0x10460e358 0x10461ed0c 0x104431f58 0x104433d18 0x10443bf24 0x109068de4 0x109070e88 0x109071b7c 0x10907bc18 0x18f1560f0 0x18f158d00)
libc++abi.dylib: terminating with uncaught exception of type NSException

Any idea why this is happening?