quickfix.Message parseGroup throws NumberFormatException

    private void parseGroup(String msgType, StringField field, DataDictionary dd, FieldMap parent)
            throws InvalidMessage {
        final DataDictionary.GroupInfo rg = dd.getGroup(msgType, field.getField());
        final DataDictionary groupDataDictionary = rg.getDataDictionary();
        final int[] fieldOrder = groupDataDictionary.getOrderedFields();
        int previousOffset = -1;
        final int groupCountTag = field.getField();
        final int declaredGroupCount;
        try {
            declaredGroupCount = Integer.parseInt(field.getValue());
        } catch(NumberFormatException nfe){
        	throw new FieldException(SessionRejectReason.INCORRECT_NUMINGROUP_COUNT_FOR_REPEATING_GROUP, "The group " + field.getTag() + " must have an integer delimiter field [value=" + field.getValue() + "]", field.getTag());
        }