Downgrade error for NoneType in get_claims

[kelockhart]

If a user has manually added a record to their ORCID profile without adding any bibcode data, and then tries to claim it in ADS, a NoneType error is produced here: https://github.com/adsabs/ADSOrcid/blob/master/ADSOrcid/app.py#L281 because the .get() returns nothing. An error may also be produced here: https://github.com/adsabs/ADSOrcid/blob/master/ADSOrcid/app.py#L272 for similar reasons. The actual error message is generated here: https://github.com/adsabs/ADSOrcid/blob/master/ADSOrcid/app.py#L319