Add missing break in a switch which caused an incorrect assertion.
Add missing break in a switch which caused an incorrect assertion.

[r14025]

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