Wrapped getUnit8() in a try...catch

Wrapping this `if` clause in a `try...catch` seems to alleviate the issue found in https://github.com/43081j/id3/issues/10 and possibly https://github.com/43081j/id3/issues/9

There seems to be no real negative impact in simply ignoring any exceptions generated by the tried code, the resulting `tags` seems to be completely fine, though a more graceful method of handling the exception should probably be implemented.