reading UUID should escalate error

[gdoteof]

https://github.com/VISIONAI/vmxmiddle/blob/master/Handler/CheckLicense.hs#L58

This line should fail if it does not properly parse the JSON

[quantombone]

I already added the fix to VMXserver to handle this kind of permission issue on my end. It would still be useful to perform another check on the vmxmiddle end, but as-is this isn't a mandatory fix...