Clearer error message if weather data is not found

I ran into a problem where I fatfingered my zip code during testing, and the error message when you ask for the `current_conditions` of a bad zip code is "object does not respond to #inspect".  I spent a little time troubleshooting before I realized the problem was in my location input.

This pull request adds a very simple rescue clause to the end of Data#inspect to clear up the nature of the problem without actually raising an exception.  It's a small change, but it might save someone down the road a few minutes of troubleshooting time.