How should we handle when SpeechSynthesis is not available?

[jessegreenberg]

I found that it felt sketchy to have a getSynth() that could return null on a platform that doesn't support speech synthesis. We have some support for that case, but I think we rely on assertions a lot to guard against null pointer exceptions. In the wild, we wouldn't have assertions so we may want to be graceful. I added a couple of spots that checked if we had a synth before calling operations on it. Does this seem correct to you? I'd hate for the sim to break just because the platform doesn't have speech synthesis. For example, in the app, right?

Currently the only platform that does not support SpeechSynthesis is Android in a WebView. So correct, this could come up in the Android app, and it has! phetsims/qa#608

I think this should hard crash and that it is up to us to not make SpeechSynthesis requests unless we are confident the platform can handle it. I almost want to replace the assertion in getSynth with an Error, I want it to let us know loudly on platforms where we expect the synth to be available but is not.

I can see both sides of the argument though. Lets talk more if you still prefer it to be graceful.

[zepumph]

This makes sense. I would prefer an Error to an assertion given your thoughts, but I still worry about getting this in production, in a case that QA hasn't tested or we don't support. Is it worth such a hard fail if we forget about a device?