Fix: 0009266: webpath to the mantis installation is calculated wrong, if mantis is installed in the root directory of a webserver

git-svn-id: http://mantisbt.svn.sourceforge.net/svnroot/mantisbt/trunk@5472 <a class="text" href="/?p=mantisbt.git;a=object;h=f5dc347c">f5dc347c</a>-c33d-0410-90a0-b07cc1902cb9