Comment 1 for bug 1536832

This is caused by a nullptr -> std::string conversion somewhere in extract_tag_info (the only match for the missing stack frame). But it is difficult to tell which conversion is the cause. There are two places where this could occur: (1) the tag name passed to the callback is NULL, or (2) a string tag value is NULL.

The second case seems more likely, so I've modified this code path in my taglib-extractor branch to add an extra NULL check. Lets see how that goes.