Accessing some variables like new_html or added_links, AbuseFilter will cause a fatal error for non-text content. This makes editing of such content impossible.
The problem is rooted in AFComputedVariable::compute(), which tries to parse text it believes to be wikitext. But for non-text content, this text may be something else entirely - typically, a plain mock of the actual page content, used for regex based filters.
The fatal error is always triggered when trying to view the log details for a filter action performed on a non-text page, since AbuseFilter will then try to evaluate all variables.