Parsing EMSG for HLS CMAF streams fails with TypeError, missing null check

[pcruiksh]

Have you read the FAQ and checked for duplicate open issues?
Yes

What version of Shaka Player are you using?
3.3.0

Can you reproduce the issue with our latest release version?
Yes

Can you reproduce the issue with the latest code from master?
Yes

Are you using the demo app or your own custom app?
custom

If custom app, can you reproduce the issue using our demo app?
y

What browser and OS are you using?
Chrome+MacOS

For embedded devices (smart TVs, etc.), what model and firmware version are you using?
n/a

What are the manifest and license server URIs?
n/a

What configuration are you using? What is the output of player.getConfiguration()?
dispatchAllEmsgBoxes

What did you do?
play HLS/CMAF stream

What did you expect to happen?
Stream plays and EMSG boxes are parsed

What actually happened?
TypeError due to null emsgSchemeIdUris (default value set by HLS parser). There is a null check in the streaming engine before calling parseEMSG_ but the config option dispatchAllEmsgBoxes supersedes it.