Fatal error when infinite recursion is detected

Because an empty array is returned on infinite recursion, the line

$result['info'] = $info + $a['info'];

in patterns_get_pattern_details() causes a fatal error because $a will be an empty array.

The attached patch causes the pattern to skip the pattern dependency instead of throwing a fatal error of
PHP Fatal error: Unsupported operand types in sites/all/modules/contrib/patterns/patterns.module on line 1823