Cast return value of `preg_replace` to `string`

[fritzmg]

preg_replace can return null when an error occurs - which would then cause the following error down the line:

TypeError:
preg_match_all(): Argument #2 ($subject) must be of type string, null given

  at vendor/codefog/contao-haste/src/StringParser.php:85

@berecont can you test if this fixes your issue?

[berecont]

Sure, the adjustment in line 79 is working.

[qzminski]

Thank you @fritzmg !