Fix LocalOut check

[telephon]

A test:

{ LocalOut.kr(0) }.asSynthDef; // works
{ LocalOut.kr([0]) }.asSynthDef; // works
{ LocalOut.kr() }.asSynthDef; // fails
{ LocalOut.kr([]) }.asSynthDef; // fails

[telephon]

With the following test, I found one more incorrectness. I'll address it in another PR:

(
var failing = [nil, []];
var working = [0, [0], [0, 0, 0]];
var stubs = [
	{ |args| LocalOut.kr(*args) },
	{ |args| Out.kr(0, *args) },
	{ |args| ReplaceOut.kr(0, *args) },
	{ |args| XOut.kr(0, 0.5, *args) },
];

var fails = failing.every { |input|
	stubs.every { |func|
		var fails = false;
		try { { func.(input) }.asSynthDef } { |err| fails = err.isException };
		if(fails.not) { "This is a case that should have failed:\n%\nOn this input:\n%\n".postf(func.cs, input) };
		fails
	}
};
var works = working.every { |input|
	stubs.every { |func|
		var works = true;
		try { { func.(input) }.asSynthDef } { |err| works = err.isException.not };
		if(works.not) { "This is a case that should not have failed:\n%\nOn this input:\n%\n".postf(func.cs, input) };
		works
	}
};

fails and: works
)

[mossheim]

Tested, works for me with the test cases you gave. Could we perhaps adapt your more rigorous test code as a unit test when you make the new PR?

[mossheim]

As stated in #2664, ready to merge once changes are made.

[mossheim]

Did this fix any open issues? I can't find any.