DuckPAN/DDG: Fixed an error with load_class.

`load_class` was returning `undef`, which makes accessing `trigger_block_type` an invalid operation. Thanks to @nilnilnil for solving the problem.
DuckPAN/DDG: Formatted code.
Merge pull request #73 from duckduckgo/jag/load

DuckPAN/DDG: Fixed an error with load_class.