Does fs_path exist?

Property definitions

linux :: audio $ PlayableAudio :: fs_path_exists
	# Does `fs_path` exist?
	private fun fs_path_exists: Bool
	do
		if not fs_path.file_exists then
			error = new Error("Failed to load audio '{path}': file not found")
			return false
		end
		return true
	end
lib/linux/audio.nit:30,2--38,4