Invalid content error in Firefox on one project

[ericrosenbaum]

@kchadha reported that on Mac Firefox, project 210672714 gives this error in the console:

The buffer passed to decodeAudioData contains invalid content which cannot be decoded successfully.

I compared the project on firefox and chrome (where there is no error), and as far as I can tell, no sounds are missing from the project, and all the sounds play correctly.