Relative directories starting with ".." will not be recognized as relative this throws NullPointer Exception during installation

We have a definition of a pack like the following:
<pack name="MyPack" id="pack.mypack.id" required="yes" preselected="yes" loose="true">
<description/>
<fileset dir="../my/pack" targetdir="$INSTALL_PATH/MyPack">
<include name="**"/>
</fileset>
</pack>

During installation we get a NPE when try to install MyPack. After a bit of debugging I found a little bug during compilation of loose packs. If a path is starting with "../" is is not recognized as a relative path and the relativePath variable in the PackFile instance is set to null.

See attached patch how to fix this problem.