Effect of playing a null AudioBuffer in an AudioBufferSourceNode, and effects of changes to 'buffer'

What happens when someone calls start(0) on an AudioBufferSourceNode while
'buffer' is null?

What happens when someone modifies 'buffer' after start() has been called?
Can this have any effect on what is played?

Rob
-- 
Jesus called them together and said, “You know that the rulers of the
Gentiles lord it over them, and their high officials exercise authority
over them. Not so with you. Instead, whoever wants to become great among
you must be your servant, and whoever wants to be first must be your
slave — just
as the Son of Man did not come to be served, but to serve, and to give his
life as a ransom for many.” [Matthew 20:25-28]