XTF1 files are not supported

[JayFoxRox]

When trying the tool on XTF1 files (from Xbox 360 backwards compatibility) it causes problems - it won't work correctly.

This tool only supports unexploited XTF0 files (from original Xbox) at the moment.
Someone should add a check for the XTF0 magic to avoid such issues in the future.

I'm not sure about the changes in XTF1, and I'm not sure if I'm willing to add support (given that XboxDev only supports the original Xbox).
If XTF1 is also found on original Xbox, then I might look into it, although the primary goal of the tool is to eventually document Ernie & Bert (XTF0).