- Check if some options have been installed before to use them
Explanation: when you upgrade the addon, the files are first replace, then the xml is used to upgrade. The options are declared inside the xml files. If an option is not yet available (not installed) XenForo will return a null value, no matter your option was declared as an array. If in your code you use this option with a php function that requires an array and instead it gets a null, then the error occurs.- Xon added an option to only do pre-caching for tags that are sufficiently used
Note that if you've upgraded to version 3.3.0 without any problems, you don't really need to do this upgrade.