What is the issue here:
==20235== Invalid write of size 4
==20235==    at 0x10928A: split_array (split_array.c:22)
==20235==    by 0x1093B5: main (split_array.c:59)
==20235==  Address 0x4a730f8 is 0 bytes after a block of size 8 alloc'd
==20235==    at 0x483B7F3: malloc (in /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so)
==20235==    by 0x109223: split_array (split_array.c:17)
==20235==    by 0x1093B5: main (split_array.c:59)