api: fix KeyError in search
    
    Exception on /api/coprs/search/tests/ [GET]
    Traceback (most recent call last):
      File "/usr/lib/python2.7/site-packages/flask/app.py", line 1687, in wsgi_app
        response = self.full_dispatch_request()
      File "/usr/lib/python2.7/site-packages/flask/app.py", line 1360, in full_dispatch_request
        rv = self.handle_user_exception(e)
      File "/usr/lib/python2.7/site-packages/flask/app.py", line 1358, in full_dispatch_request
        rv = self.dispatch_request()
      File "/usr/lib/python2.7/site-packages/flask/app.py", line 1344, in dispatch_request
        return self.view_functions[rule.endpoint](**req.view_args)
      File "/usr/share/copr/coprs_frontend/coprs/views/api_ns/api_general.py", line 409, in api_coprs_search_by_project
        output["repos"].append({"username": repo.owner,
    KeyError: 'repos'
    
    Signed-off-by: Richard Marko <rmarko@fedoraproject.org>