DirectiveSet::canNotBeFallbackedByDefault(): Argument #2 ($value) must be of type string, bool given

[bartosz-zolynski]

While updating Nelmio bundle from 2.12.0 to 3.0.0, it seems that passing boolean to block-all-mixed-content breaks the functionality as string is expected:

Nelmio\SecurityBundle\ContentSecurityPolicy\DirectiveSet::canNotBeFallbackedByDefault(): Argument #2 ($value) must be of type string, bool given, called in /var/www/vendor/nelmio/security-bundle/src/ContentSecurityPolicy/DirectiveSet.php on line 146

Part of the config that follows the current documentation:

nelmio_security:
  csp:
    enforce:
      block-all-mixed-content: true

Not sure if this also impacts other keys used by this functionality.