Show signatures that don't belong to any page in the signature panel
Needs poppler 0.88, we "pretend" the belong to page 0 since in Okular core there's no concept of having a signature that doesn't belong to any page
Needs poppler 0.88, we "pretend" the belong to page 0 since in Okular core there's no concept of having a signature that doesn't belong to any page