Gracefully handle DB2 parsing issues

[Kruithne]

Currently if an issue is encountered during the loading of a data table, an error is thrown. This should instead be handled gracefully by always returning a table, even if it's empty. In the event of an error, a partial or empty table is acceptable.

Throughout the application, uses of data tables should implement logic conscious to the idea that a data table may be empty for any reason, and handle that gracefully. The addition of this logic as well as necessary UI changes to indicate to the user that data is missing is not necessarily within the scope of this issue, but an extension upon it for further development.

[Marlamin]

Also, if possible, this should try redownloading the DBD and retrying parsing just in case it's an outdated definition like #382