UPDATE: Problem partly solved when I switch from Premium version to Free. Problem that solved partly is errors about preg_split in ACP. Thats weird :/
The issue does not seem to be related to my plugin. The error you mentioned appears to be within the convert_smilies function, even though the line number is not accurate, indicating that WordPress might not be updated to the latest version. This problem suggests that the text of one of the comments is NULL, which does not occur during all my tests.
If you still think that my plugin is causing the issue, I’m going to need more information about your system, such as PHP version, WP version and all installed themes and plugins.
During the investigation of this report, I identified another bug related to comments and have released a patch to address it.