Unmaintained Conversation Improvements by Xon 1.3.15

• Do not index conversations with no recipients. This was causing an error as it was assumed all conversations had valid/active recipients or where deleted.

• Fix an error when checking permissions to view conversation search results.
• Fix potential error when fetching zero conversations/conversations messages (normal code will not hit this).
  
  

• Allow users with the 'Manage Conversation' permission but without the 'Edit post by anyone' permission to restore conversation messages from history for their own posts.

• Fix error when a user reverts their own conversation message when they have the 'Manage Conversation' permission without the 'Edit post by anyone' permission.
• Change default for "Allow conversations with no-one" to Off.

Allow conversations with no-one

New global option to allow conversations without any recipients.
Controllable under Options "Threads, Discussions and Conversations" -> Conversation with no-one

• Missed disabling the add-on in the case of when an account is renamed/merged and a deferred cleanup task runs.

• Prevent errors when add-on is disabled, by ensuring content handlers exit out rather than error.
  

Fix typo in sv_conversation_started_by_x_date_y phrase

Thanks @sadiq6210

• When viewing a conversation, the conversation start date is now correctly displayed under the title.

• Update schema to prevent errors view conversations when the add-on is disabled or uninstalled.
  • Argument 4 passed to XenForo_Template_Helper_Core::helperLikesHtml() must be of the type array, null given
• Remove all schema changes and data created by the add-on on uninstall.