tagging "8½ Minutes" with "replace with non-ascii characters" results in a directory being created

track: http://musicbrainz.org/recording/ada94805-940e-44ca-b3a9-3e4602626c43

Tagging this track resulted in Picard attempting to name the file "11 81/2 Minutes.flac", which turned into a directory named "11 81" with a file named "2 Minutes.flac" inside it.

Looks like Picard can catch a "/" and replace it with "_" when it's actually in the string, but the replacement of "1/2" for "½" is slipping past that filter.

Expected behavior: Picard replaces "½" with "1/2" and then replaces "1/2" with "1_2" when it's written as a filename. If the "½" to "1/2" replacement never happens outside of the filename context (I'm not sure), then just change that substitution to "1_2".