Merge pull request #893 from RosettaCommons/vmullig/fix_sewing_hasher_tests
Fixing app_exception_handling AGAIN.
This is the danger of letting an integration test sit around in a broken state: when people check in additional code that ALSO breaks what the integration test is meant to test, they don't know that they've done something wrong. Because Rhiju's gaussian_chain_func_test was causing app_exception_handling to fail, two more apps slipped in under the radar without try/catch blocks.
The struc_set_fragment_picker app, which was newly-added, had no try/catch block. Fixed now in this pull request.