Gracefully handle reports without links

[rdmurphy]

http://www.ethics.state.tx.us/php/filer.php?acct=00051772

Nothing will ever successfully pull here. You'll be able to get the filing list, but that's it. Currently having to catch the KeyError on 'CVR' to prevent things from breaking.

[rdmurphy]

By the way – this is only happening on .save() calls, which triggers multiple queries on the Report model. Normally a Filing will know if it can be downloaded or not ('is_downloadable' == False), but a Filing.report should throw a more helpful error so you can address it properly.