[mod] allow whitespaces in category/engine list

            load_default_categories = True

            for pd_name, pd in self.request_data.items():

                if pd_name == 'categories':

                    self.categories.extend(categ for categ in pd.split(',') if categ in categories)

                    self.categories.extend(categ.strip() for categ in pd.split(',') if categ in categories)

                elif pd_name == 'engines':

                    pd_engines = [{'category': engines[engine].categories[0],

                                   'name': engine}

                                  for engine in pd.split(',') if engine in engines]

                                  for engine in map(str.strip, pd.split(',')) if engine in engines]

                    if pd_engines:

                        self.engines.extend(pd_engines)

                        load_default_categories = False