bugfix: wrong test command parameters

files/startup

@@ -15,10 +15,10 @@ beginLogEntry "install default dependencies"
 installPackages bash parted bc ntfs-3g dosfstools openssl btrfs-progs e2fsprogs blkid curl
 finishLogEntry "done"
 
-if [ -z ${answerfile_baseurl} -a -z ${ANSWERFILE_URL} ];
+if [ "x${answerfile_baseurl}" = "x" -a "x${ANSWERFILE_URL}" = "x" ];
 then
   read -p "Please enter the answer file URL: " ANSWERFILE_URL
-elif [ -n ${answerfile_baseurl} ];
+elif [ "x${answerfile_baseurl}" != "x" ];
 then
   ANSWERFILE_URL=${answerfile_baseurl}
 fi