get_irn_MacroBlock(): if the Block of a node is Bad, do NOT try to returns its MB, return Bad.
get_irn_MacroBlock(): if the Block of a node is Bad, do NOT try to returns its MB, return Bad.

[r17201]

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