PrintNode::viewScales does not work when $deviceNumber is not NULL

[archonia-chris]

public function viewScales($computerId, $deviceName = null, $deviceNumber = null)

When $deviceNumber is anything but NULL, the following URL is created

"/computer/{$computerId}/scales/{$deviceName}/{$deviceNumber}"

This is not a valid API url ("scales" vs "scale"):

GET/computer/COMPUTER ID/scales
GET/computer/COMPUTER ID/scales/DEVICE NAME
GET/computer/COMPUTER ID/scale/DEVICE NAME/DEVICE NUMBER

A 404 is returned.

Additionally, ResponseprocessResponseString generates an error since $this->bodyJson is NULL in such a case
throw new Exception\HTTPException($this->httpStatusCode, $this->bodyJson->message);