checked for dead blocks before getting dom depht.
checked for dead blocks before getting dom depht.

[r6567]

MatzeB/libfirm,MatzeB/libfirm,libfirm/libfirm,8l/libfirm,davidgiven/libfirm,killbug2004/libfirm,davidgiven/libfirm,davidgiven/libfirm,killbug2004/libfirm,MatzeB/libfirm,libfirm/libfirm,jonashaag/libfirm,davidgiven/libfirm,davidgiven/libfirm,jonashaag/libfirm,MatzeB/libfirm,8l/libfirm,davidgiven/libfirm,killbug2004/libfirm,8l/libfirm,jonashaag/libfirm,killbug2004/libfirm,killbug2004/libfirm,libfirm/libfirm,libfirm/libfirm,killbug2004/libfirm,MatzeB/libfirm,jonashaag/libfirm,jonashaag/libfirm,8l/libfirm,MatzeB/libfirm,libfirm/libfirm,8l/libfirm,8l/libfirm,8l/libfirm,MatzeB/libfirm,davidgiven/libfirm,jonashaag/libfirm,jonashaag/libfirm,killbug2004/libfirm