Make sure get_param_list returns empty list if param is missing
Make sure get_param_list returns empty list if param is missing

If the specified parameter was missing from `$c->req->params`, a list
of form `(undef)` would be returned. This commit makes it return an
empty list if the parameter is missing.

mhalden/fixmystreet,appstud/fixmystreet,rbgdigital/fixmystreet,mhalden/fixmystreet,antoinepemeja/fixmystreet,nditech/fixmystreet,otmezger/fixmystreet,dracos/fixmystreet,rbgdigital/fixmystreet,otmezger/fixmystreet,antoinepemeja/fixmystreet,altinukshini/lokalizo,nditech/fixmystreet,altinukshini/lokalizo,appstud/fixmystreet,dracos/fixmystreet,appstud/fixmystreet,otmezger/fixmystreet,antoinepemeja/fixmystreet,appstud/fixmystreet,mhalden/fixmystreet,mhalden/fixmystreet,otmezger/fixmystreet,nditech/fixmystreet,antoinepemeja/fixmystreet,rbgdigital/fixmystreet,otmezger/fixmystreet,dracos/fixmystreet,rbgdigital/fixmystreet,rbgdigital/fixmystreet,appstud/fixmystreet,rbgdigital/fixmystreet,antoinepemeja/fixmystreet,altinukshini/lokalizo,nditech/fixmystreet,antoinepemeja/fixmystreet,altinukshini/lokalizo,antoinepemeja/fixmystreet,dracos/fixmystreet,nditech/fixmystreet,mhalden/fixmystreet,altinukshini/lokalizo,otmezger/fixmystreet,dracos/fixmystreet,nditech/fixmystreet,appstud/fixmystreet,dracos/fixmystreet,appstud/fixmystreet,mhalden/fixmystreet,altinukshini/lokalizo,nditech/fixmystreet,otmezger/fixmystreet