Can Burak Cilingir, until the maintainer finds time to fix this, you could try the attached patch. I believe that somehow cleantmp() is being called while $TMPTIME is undefined. Did you modify /etc/default/rcS and set it to something invalid? If it is set to "", then the attached patch will make bootclean.sh fall back to the default of zero. It's not foolproof; you will still have problems if TMPTIME is set to " " or something similar.
28c28 < if [ "$TMPTIME" = 0 ] --- > if [ -z "$TMPTIME" -o "$TMPTIME" = 0 ] 56c56 < ( if cd /tmp && [ "`find . -perm -002 -maxdepth 0`" = "." ] --- > ( if cd /tmp && [ "`find . -maxdepth 0 -perm -002`" = "." ] 59,60c59,60 < find . -xdev $TEXPR $EXCEPT \ < ! -type d -depth -print0 | xargs -0r rm -f --- > find . -xdev -depth $TEXPR $EXCEPT \ > ! -type d -print0 | xargs -0r rm -f 62,63c62,63 < find . -xdev $DEXPR $EXCEPT \ < -type d -depth -empty -exec rmdir \{\} \; --- > find . -xdev -depth $DEXPR $EXCEPT \ > -type d -empty -exec rmdir \{\} \;