udf: Fix uninitialized array access for some pathnames

In the Linux kernel, the following vulnerability has been resolved: udf: Fix uninitialized array access for some pathnames For filenames that begin with . and are between 2 and 5 characters long, UDF charset conversion code would read uninitialized memory in the output buffer. The only practical impact is that the name may be prepended a "unification hash" when it is not actually needed but still it is good to fix this.