This error message indicates that the node is running Out Of Memory. This could be the result of a bug in the code, or memory requirements for the given input. Note that due to optimistic memory allocation, you probably will not get a null pointer, even if you are out of memory. The program should be killed at the point the memory is used.
One quick solution might be to run with only four MPI processes per socket so each process gets a larger share of the memory on the node:
-S 4 ./a.out
-S 2). The best solution may be to identify the memory requirements in the code and make any necessary changes there, in terms of memory parameters, domain decomposition, etc.