Drop firefox empty string candidates

[athouary]

Initial issue: otalk/sdp-jingle-json#29

These changes will prevent the error TypeError: parts[2] is undefined from occurring when Firefox uses empty string candidates that can't be parsed properly.

[nels83]

According to MDN : https://developer.mozilla.org/en-US/docs/Web/API/RTCIceCandidate/candidate an empty string "is known as the "end-of-candidates" marker".

Maybe changing
if (event.candidate) {
to
if (event.candidate && event.candidate.candidate.length) {

should be better since it will emit endOfCandidates ?

[athouary]

I believe I tested what you are suggesting and got unexpected results, but I'm not so sure anymore, even though it does sound like the right thing to do.

I'm not sure that I'll take the time to update the PR since I worked around the issue by not using the RTCPeerConnection module anymore, so feel free to create another PR if you want your suggested change to be merged.