Online Audio Sys Des Tool doc update for getBuffer(); add available();

[Defragster]

Description

Error in and Undocumented functions on https://www.pjrc.com/teensy/gui/?info=AudioPlayQueue
AudioPlayQueue details getBuffer(); suggesting it will return NULL, but it will not. Also the available(); function is not documented

Steps To Reproduce Problem

See https://forum.pjrc.com/threads/53860-Audio-play_qeue()-documentation

Not seeing where the source lives - this is a suggested text change spotted by Frank_B with his review of forum posted text.

[FrankBoesing]

2254de0

[Defragster]

Nice Frank - I didn't take the next step to locate the source lines.

Audio/gui/index.html

Line 1757 in 2254de0

A single 'userblock' is maintained for this object.