attachMediaStream does not accept null as second parameter on Firefox

[pg94au]

When I try using rtcninja.js v0.6.3, I'm seeing a problem with Firefox when I call attachMediaStream with null as the stream parameter to remove the stream from a video element. This works for Chrome and IE with Temasys, but not Firefox. In Firefox 40.0.3, when rtcninja calls URL.createObjectURL with a null stream, it produces the following error:

14:15:39.505 TypeError: Argument 1 is not valid for any of the 2-argument overloads of URL.createObjectURL.

If I call attachMediaStream directly, it succeeds in Chrome, IE/Temasys and Firefox.

[ibc]

Thanks. I'll take a look at this next week.