Comment # 5 on bug 839492 from Dominique Leuenberger

(In reply to Ruediger Oertel from comment #3)
> argh, that code is buggy:
> 
> +if [ -x $(type -p xmllint) ]; then
> 
> if not installed, $(type -p xmllint) expands to ""
> and if [ -x ""] is always true ...

At least according 'man test', this is not true:

[...]
       -x FILE
              FILE exists and execute (or search) permission is granted
[...]

Also, in my tests, this has proven to be correct.