redis-check-dump: Prevent segfault if can't malloc
redis-check-dump: Prevent segfault if can't malloc

Found by The Mayhem Team (Alexandre Rebert, Thanassis Avgerinos,
Sang Kil Cha, David Brumley, Manuel Egele) Cylab, Carnegie Mellon
University. See http://bugs.debian.org/716259 for more.

Signed-off-by: Chris Lamb <lamby@debian.org>

Fixes #1191

laurencee/redis,jqk6/redis,fanxu/redis,kts12345/redis,ideaar/redis,erwin00776/redis-2.8-optimize,jacklee0810/redis,ideaar/redis,nandhanurrevanth/redis,alpha8/redis,jaambee/redis,janeasystems/redis,sidsen/redis,laurencee/redis,upsoft/redis,kts12345/redis,jacklee0810/redis,LittlePeng/redis,Jonavin/redis,quangnguyen90/redis,hanmichael/redis,Cybermaxs/redis,miminus/redis,sidsen/redis,jacklee0810/redis,kolonse/redis,nandhanurrevanth/redis,jqk6/redis,adamweixuan/redis,enginekit/redis,quangnguyen90/redis,jqk6/redis,janeasystems/redis,hanmichael/redis,alpha8/redis,nandhanurrevanth/redis,damy/redis,sidsen/redis,jacklee0810/redis,alpha8/redis,erwin00776/redis-2.8-optimize,jqk6/redis,jaambee/redis,ScottKaiGu/redis,shanegxxiao/redis,damy/redis,fanxu/redis,alpha8/redis,adamweixuan/redis,jqk6/redis,StartTheShift/redis-shift,StartTheShift/redis-shift,sidsen/redis,shanegxxiao/redis,adamweixuan/redis,fanxu/redis,jacklee0810/redis,liqiang199105/redis,nandhanurrevanth/redis,enginekit/redis,liqiang199105/redis,ScottKaiGu/redis,kts12345/redis,ScottKaiGu/redis,erwin00776/redis-2.8-optimize,liqiang199105/redis,hanmichael/redis,quangnguyen90/redis,damy/redis,laurencee/redis,quangnguyen90/redis,ideaar/redis,jaambee/redis,Cybermaxs/redis,upsoft/redis,damy/redis,liqiang199105/redis,sidsen/redis,upsoft/redis,alpha8/redis,shanegxxiao/redis,LittlePeng/redis,miminus/redis,kolonse/redis,quangnguyen90/redis,fanxu/redis,upsoft/redis,adamweixuan/redis,Cybermaxs/redis,damy/redis,adamweixuan/redis,liqiang199105/redis,enginekit/redis,kts12345/redis,ideaar/redis,jaambee/redis,erwin00776/redis-2.8-optimize,ScottKaiGu/redis,enginekit/redis,kolonse/redis,kolonse/redis,shanegxxiao/redis,ideaar/redis,Jonavin/redis,shanegxxiao/redis,Jonavin/redis,kts12345/redis,Jonavin/redis,janeasystems/redis,jaambee/redis,miminus/redis,upsoft/redis,LittlePeng/redis,ScottKaiGu/redis,Cybermaxs/redis,enginekit/redis,kolonse/redis,StartTheShift/redis-shift,janeasystems/redis,nandhanurrevanth/redis,miminus/redis,laurencee/redis,hanmichael/redis,Jonavin/redis,janeasystems/redis,laurencee/redis,sidsen/redis,Cybermaxs/redis,hanmichael/redis,miminus/redis