[PATCH] dynahash: add memory allocation failure check

Hi all,
I found a case of potential NULL pointer dereference.
In src/backend/utils/hash/dynahash.c in function HTAB *hash_create() the 
result of the DynaHashAlloc() is used unsafely.
The function DynaHashAlloc() calls MemoryContextAllocExtended() with 
MCXT_ALLOC_NO_OOM and can return a NULL pointer.
Added the pointer check for avoiding a potential problem.
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Best regards, Korotkov Maksim
PostgresPro
m.korotkov@postgrespro.ru