If the "fullURL" parameter to checkForReload has a URL string that isNull (for example, it was generated by resolving a relative URL on a data: base URL), this function will crash in cache()->resourceForURL(fullURL.url()). I don't know whether the cache should handle NULL strings, or whether checkForReload should filter them out first. This crash doesn't happen in practice because of another bug I am about to file.
http://trac.webkit.org/projects/webkit/changeset/30243