Hello, I have a schema.json like below, and when I try to validate my json (also below) I'm receiving the Exception from the title. **schema.json**: ```json { "$schema": "http://json-schema.org/schema#", "type": "string", "pattern": "^\\#ref\\(.+\\)$" } ``` **json**: ```json "ref" ``` Investigating the StringConstraint.php, on line 42 it has this code: ```php if (isset($schema->pattern) && !preg_match('#' . str_replace('#', '\\#', $schema->pattern) . '#u', $element)) { ``` which is replacing `#` by `\\#` and concatenating everything with `#`-prefix and `#u`-suffix. Am I going something wrong or is it a bug?