bugfix: #1855 - PHP errors from non-Lyrics3-aware APE tagging software

http://www.getid3.org/phpBB3/viewtopic.php?t=1855
If a MP3 file is tagged with Lyrics3, and then re-tagged with APE tags
using software that is not aware of Lyrics3 tags then both Lyrics3 and
APE tags could become corrupted.