Import from SongSelect no longer works (website updated)

Same for Ubuntu 16.04 and Windows 8.1.

Under Ubuntu with openlp 2.4.3 runs the ccli import search in endless loop. Try it with "ocean". I killed the search after 650 results...

I know this is an old bug and it was fixed in between, but it's back.

Trying to import songs from CCLI, I get
"There was a problem logging in, perhaps your username or password is incorrect?"

Happens on both Windows 10 and Ubuntu 16.04, both running 2.4.5.

Yes, we know.

Fix intermittently but now breaks on search (after login).

I don't know how to submit a PR on launchpad, but adding a `or is None` on line 130 of `html.__init__.py` in `unescape()` fixed it. It now reads

```python
if '&' not in s or s is None:
    return s
return _charref.sub(_replace_charref, s)
```

That's Python's code, not ours, but it probably means we need to filter the string before it goes to unescape().

Fix committed