Error in tool_offsetview.py

Pushed.
Thank you!

The preview window has a similar problem to the Vismach. There's no limit at all to the maximum and minimum zoom. You can zoom in infinitely without any visual effect, and the same applies to zooming out. There's also a tweak to the s value, which doesn't work linearly with zooming in and out, and at certain zoom levels, moving left, right, and up is difficult.

I'm uploading the corrected glnav.py.
Please try it out.

Works great for me.
Pushed.

Thanks