Fix a crashing case where arena_chunk_init_hard returns NULL.
Fix a crashing case where arena_chunk_init_hard returns NULL.

This happens when it fails to allocate a new chunk. Which
arena_chunk_alloc then passes into arena_avail_insert without any
checks. This then causes a crash when arena_avail_insert tries
to check chunk->ndirty.

This was introduced by the refactoring of arena_chunk_alloc
which previously would have returned NULL immediately after
calling chunk_alloc. This is now the return from
arena_chunk_init_hard so we need to check that return, and
not continue if it was NULL.

ahmetmircik/jemalloc,AndroidExternal/jemalloc,wespelee/jemalloc,wqfish/jemalloc,8l/jemalloc,ahmetmircik/jemalloc,wqfish/jemalloc,CMRemix/android_external_jemalloc,xin3liang/platform_external_jemalloc,lilothar/jemalloc,ahmetmircik/jemalloc,CyanogenMod/android_external_jemalloc,lvfeng1130/jemalloc,TeamExodus/external_jemalloc,CyanogenMod/android_external_jemalloc,wfxiang08/jemalloc,android-ia/platform_external_jemalloc,CMRemix/android_external_jemalloc,tempbottle/jemalloc,wfxiang08/jemalloc,geekboxzone/mmallow_external_jemalloc,kmiku7/jemalloc,xin3liang/platform_external_jemalloc,garoose/jemalloc,Snaipe/jemalloc,cpeterso/jemalloc,Snaipe/jemalloc,lvfeng1130/jemalloc,wespelee/jemalloc,CyanogenMod/android_external_jemalloc,jemalloc/jemalloc-cmake,yy-nm/jemalloc,sudosurootdev/external_jemalloc,Dmitry-Me/jemalloc,flyfeifan/jemalloc,garoose/jemalloc,TeamExodus/external_jemalloc,android-ia/platform_external_jemalloc,cpeterso/jemalloc,yy-nm/jemalloc,dxq-git/jemalloc,CMRemix/android_external_jemalloc,glandium/jemalloc,leebaok/jemalloc-4.2.1-readcode,wqfish/jemalloc,VRToxin/android_external_jemalloc,xin3liang/platform_external_jemalloc,geekboxzone/mmallow_external_jemalloc,lvfeng1130/jemalloc,Dmitry-Me/jemalloc,tempbottle/jemalloc,kmiku7/jemalloc,lilothar/jemalloc,VRToxin/android_external_jemalloc,lvfeng1130/jemalloc,sudosurootdev/external_jemalloc,glandium/jemalloc,yy-nm/jemalloc,wespelee/jemalloc,8l/jemalloc,leebaok/jemalloc-4.2.1-readcode,lilothar/jemalloc,jemalloc/jemalloc-cmake,flyfeifan/jemalloc,wfxiang08/jemalloc,awreece/jemalloc,glandium/jemalloc,cpeterso/jemalloc,tempbottle/jemalloc,TeamExodus/external_jemalloc,sudosurootdev/external_jemalloc,xin3liang/platform_external_jemalloc,vashstorm/jemalloc,jemalloc/jemalloc-cmake,shekkbuilder/jemalloc,yy-nm/jemalloc,AndroidExternal/jemalloc,geekboxzone/mmallow_external_jemalloc,shekkbuilder/jemalloc,geekboxzone/lollipop_external_jemalloc,vashstorm/jemalloc,geekboxzone/lollipop_external_jemalloc,geekboxzone/lollipop_external_jemalloc,geekboxzone/mmallow_external_jemalloc,Dmitry-Me/jemalloc,dxq-git/jemalloc,vashstorm/jemalloc,Snaipe/jemalloc,AndroidExternal/jemalloc,awreece/jemalloc,awreece/jemalloc,leebaok/jemalloc-4.2.1-readcode,cpeterso/jemalloc,garoose/jemalloc,wfxiang08/jemalloc,leebaok/jemalloc-4.2.1-readcode,dxq-git/jemalloc,garoose/jemalloc,wespelee/jemalloc,geekboxzone/lollipop_external_jemalloc,8l/jemalloc,AndroidExternal/jemalloc,flyfeifan/jemalloc,CyanogenMod/android_external_jemalloc,CMRemix/android_external_jemalloc,VRToxin/android_external_jemalloc,wqfish/jemalloc,awreece/jemalloc,android-ia/platform_external_jemalloc,flyfeifan/jemalloc,shekkbuilder/jemalloc,dxq-git/jemalloc,lilothar/jemalloc,android-ia/platform_external_jemalloc,kmiku7/jemalloc,TeamExodus/external_jemalloc,Snaipe/jemalloc,shekkbuilder/jemalloc,tempbottle/jemalloc,8l/jemalloc,sudosurootdev/external_jemalloc,kmiku7/jemalloc,VRToxin/android_external_jemalloc,Dmitry-Me/jemalloc,jemalloc/jemalloc-cmake,ahmetmircik/jemalloc,vashstorm/jemalloc,wqfish/jemalloc,glandium/jemalloc