I expect, but haven’t checked, that this is a more of an ambiguity than a bug, and that the ambiguity can only be resolved at the host end. If the processBlock isn’t being called there’s nothingJUCE can do to force the host to accept audio data…
some hosts (like ours AGENT) detect when no audio is passing through it and disable it, you can create whitenoise at -100 or something decibels and that should be enough, or make it a synth, that way all hosts will call your processblock