Fix "Call to a member function setAsSaved() on false" error.

• Allow staff users to set a separate signature for help desk replies.
• Display open and total ticket counts on the category list when viewing the ticket queue.
• Add a style property to toggle how ticket counts should be displayed on the category list.
• Fix not being able to delete attachments from ticket messages.
• Fix not being able to unlock locked tickets from the ticket edit page.
• Fix anonymised staff replies would cause the first message of a ticket to be indexed as a guest instead of the actual user or the anonymised account.
• Fix quotes/mentions from anonymised messages attributed to the ticket starter.
• Fix an issue preventing audio/video content being uploaded to knowledge base articles.
• Fix duplicate images potentially showing in the knowledge base articles attachment lightbox.
• Various bits of code clean up.

• Add category option to alert email addresses when a ticket is opened in that category.
• Add priority option to alert email addresses when a ticket is opened with that priority.
• Add ability to set business hours. Use this with notices to communicate that replies may be delayed out of hours.
• When upgrading from the XenForo 1 version, don't overwrite the first category's properties.
• Assorted improvements and fixes for anonymised ticket messages.
• Emails that fail to be parsed are no longer deleted.
• Skip triggering escalations when a reply is made via escalation.

• Fix "Watched tickets" link showing for guest users.
• Fix staff reply check when guest users reply to a ticket.

• Add support for XenForo 2.3+.
• Require PHP 8.0+.
• Require Standard Library by Xon v1.21.0+.
• Add support for rejected and disabled users to create tickets.
• Add support for silently editing ticket messages.
• Add support for uploading audio/video files to ticket messages.
• Add support for uploading audio/video files to knowledge base articles.
• Add webhook support for tickets and ticket messages. XF 2.3+ only.
• Add tracking for basic ticket statistics.
• Add option to hide categories from the new ticket chooser but still allow tickets to be created within them.
• Add options to statuses to transition tickets to another status depending on staff or user reply.
• Code clean up.