Add-ons Addon Update Notifier 1.1.8 Patch Level 1

• Some add-ons (unclear which, but only seems to have affected some forums) apparently have some magical addon.json format that broke the collection of add-ons for checking.
• This fixed version checks that the specific addon.json values are strings (as they should be) before trying to use them, to ensure that it doesn't crash.

• Previous version checked for exact add-on url, which doesn't work in case an add-on has changed URL (title)
• New version checks with the slug id so it is still matching correct add-on when a developer changes their add-on name

• Note: This is a backend change, meaning: there is no new package to install
• Since XF2.3 the pages have <time>-elements with slightly different markup to denote timestamps.
• Our backend is now updated to correctly read the timestamp for add-on updates