memory lost debug from Valgrind

[zhaoxiao9302]

I use Valgrind to find the memory leak of OCTP.
Here is what I got.

==50788==
==50788== HEAP SUMMARY:
==50788== in use at exit: 6 bytes in 3 blocks
==50788== total heap usage: 36,781 allocs, 36,778 frees, 409,449,169 bytes allocated
==50788==
==50788== 6 bytes in 3 blocks are definitely lost in loss record 1 of 1
==50788== at 0x4C2B1C9: operator new[](unsigned long) (vg_replace_malloc.c:423)
==50788== by 0x88C157: LAMMPS_NS::FixOrderN::FixOrderN(LAMMPS_NS::LAMMPS*, int, char**) (fix_ordern.cpp:131)
==50788== by 0x82AD00: LAMMPS_NS::Fix* LAMMPS_NS::Modify::fix_creator<LAMMPS_NS::FixOrderN>(LAMMPS_NS::LAMMPS*, int, char**) (modify.cpp:961)
==50788== by 0x81B616: LAMMPS_NS::Modify::add_fix(int, char**, int) (modify.cpp:892)
==50788== by 0x473B31: LAMMPS_NS::Input::execute_command() (input.cpp:809)
==50788== by 0x474196: LAMMPS_NS::Input::file() (input.cpp:243)
==50788== by 0x405925: main (main.cpp:64)
==50788==
==50788== LEAK SUMMARY:
==50788== definitely lost: 6 bytes in 3 blocks
==50788== indirectly lost: 0 bytes in 0 blocks
==50788== possibly lost: 0 bytes in 0 blocks
==50788== still reachable: 0 bytes in 0 blocks
==50788== suppressed: 0 bytes in 0 blocks
==50788==
==50788== For counts of detected and suppressed errors, rerun with: -v
==50788== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)

From this report, line 131 of fix_ordern caused the problem.
How can we fix it?