error in demo

[pankiwi]

Error

media.lua:18: bad argument #2 to 'newSource' (string expected, got no value)

Traceback

[love "callbacks.lua"]:228: in function 'handler'
[C]: in function 'newSource'
media.lua:18: in function 'newSource'
media.lua:32: in function 'load'
main.lua:24: in function 'load'
[love "callbacks.lua"]:136: in function <[love "callbacks.lua"]:135>
[C]: in function 'xpcall'
[C]: in function 'xpcall'