[Medium Priority] hideParticles no longer works in the /effect command

Verification builds:

1.2 Release_459200

Summary:
When I run a command such as "/effect @p regeneration 200 200 true", the final argument "hideParticles" seems to be ignored. This is a bug that is newly affecting Release_459200 and did not affect Release_453415. I get black particles around me no matter what.

Impact:
If we try and do something discreetly, there are now annoying particles flying in our player's faces. Also makes it very difficult for us to work.

What is the impact to players/partners if we don't fix?
A messy map which is hard to see.

Repro Steps:
Run any effect command with "true" as the hideParticles argument

Observed Results:
Black particles in the face

Expected Results:
No particles at all