These are harmless and really only for debugging. So remove them
as they tend to trick people in to thinking something is wrong.
We already print the entire server pixel format earlier anyway in
case we need the details.
Commit 6e7e6f9 stopped the function from running if width or height was
zero, this commit reverts that change. This commit also makes the
resulting canvas 0x0 if autoscale is called with zero. By adding this
special case we can avoid division by zero in the calculations.
It is not necessary as Websock.flush() is guaranteed to succeed and
give us some space. It also remove the call to _fail(), which was
invalid at this place as clientCutText() is not a method on RFB.
We accidentally removed the code updating the data index in 8a189a6,
resulting in the decoder newer consuming any data. So the data would
be parsed as the next rect, causing weird errors.
