[PATCH] mm/memblock.c: fix NULL dereference error

[zijun_hu]

This is a multi-part message in MIME format.Hi Andrew,

this patch is part of https://lkml.org/lkml/2016/7/26/347 and isn't merged in
as you advised in another mail, i release this patch against linus's mainline
for fixing relevant bugs completely, see test patch attached for verification
details