Tidy up csv parsing for groups

lib/brexit_checker/convert_csv_to_yaml/actions_processor.rb

@@ -23,7 +23,7 @@ def process(record)
         stripped_record = parse_logic_fields(stripped_record)
         stripped_record = strip_trailing_whitespace(stripped_record)
         stripped_record = remove_empty_fields(stripped_record)
-        stripped_record = parse_grouping(stripped_record)
+        stripped_record["result_groups"] &&= stripped_record["result_groups"].split(",").map(&:strip)
         stripped_record["priority"] = stripped_record["priority"].to_i
         stripped_record
       end
@@ -36,12 +36,6 @@ def parse_logic_fields(record)
         end
       end
 
-      def parse_grouping(record)
-        group_criteria = record["result_groups"]
-        record["result_groups"] = group_criteria.split(",").map(&:strip) unless group_criteria.nil?
-        record
-      end
-
       def remove_unnecessary_fields(record)
         record.keep_if { |k, _v| ALLOWED_FIELDS.include?(k) }
       end