generate DOGETEST address from XPUB

When I want to generate dogetest address from xpub i got this error messge:

```
site-packages\hdwallet\utils.py", line 343, in is_root_xpublic_key
    semantic.upper()
AttributeError: 'NoneType' object has no attribute 'upper'
```
I used this example:
https://github.com/meherett/python-hdwallet/blob/master/examples/from_xpublic_key.py
