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.