heap buffer overflow with invalid .zsh_history file

[juppytt]

➜  hstr-ori git:(master) ✗ ./src/hstr -n 
=================================================================
==123306==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x6020000003f2 at pc 0x55a873ba9774 bp 0x7ffc36045bc0 sp 0x7ffc36045bb8
READ of size 1 at 0x6020000003f2 thread T0
    #0 0x55a873ba9773  (/home/juhee/project/foxfuzz/programs/file/hstr-ori/src/hstr+0x119773)
    #1 0x55a873ba9ce7  (/home/juhee/project/foxfuzz/programs/file/hstr-ori/src/hstr+0x119ce7)
    #2 0x55a873bb95e0  (/home/juhee/project/foxfuzz/programs/file/hstr-ori/src/hstr+0x1295e0)
    #3 0x55a873bb9cad  (/home/juhee/project/foxfuzz/programs/file/hstr-ori/src/hstr+0x129cad)
    #4 0x7f3ba0e06082  (/usr/lib/x86_64-linux-gnu/libc.so.6+0x24082) (BuildId: 1878e6b475720c7c51969e69ab2d276fae6d1dee)
    #5 0x55a873ab159d  (/home/juhee/project/foxfuzz/programs/file/hstr-ori/src/hstr+0x2159d)

0x6020000003f2 is located 0 bytes to the right of 2-byte region [0x6020000003f0,0x6020000003f2)
allocated by thread T0 here:
    #0 0x55a873b62577  (/home/juhee/project/foxfuzz/programs/file/hstr-ori/src/hstr+0xd2577)
    #1 0x7f3ba123500c  (/usr/lib/x86_64-linux-gnu/libreadline.so.8+0x3c00c) (BuildId: b26b37d04de63161632027760514b3256bf2062d)

SUMMARY: AddressSanitizer: heap-buffer-overflow (/home/juhee/project/foxfuzz/programs/file/hstr-ori/src/hstr+0x119773) 
Shadow bytes around the buggy address:
  0x0c047fff8020: fa fa fd fa fa fa 00 04 fa fa fd fd fa fa fd fd
  0x0c047fff8030: fa fa fd fd fa fa fd fd fa fa fd fd fa fa 03 fa
  0x0c047fff8040: fa fa 04 fa fa fa 03 fa fa fa 06 fa fa fa 05 fa
  0x0c047fff8050: fa fa 03 fa fa fa 03 fa fa fa 04 fa fa fa 05 fa
  0x0c047fff8060: fa fa 04 fa fa fa 07 fa fa fa 06 fa fa fa 04 fa
=>0x0c047fff8070: fa fa 04 fa fa fa fd fa fa fa 00 04 fa fa[02]fa
  0x0c047fff8080: fa fa 00 fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff8090: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff80a0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff80b0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff80c0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
Shadow byte legend (one shadow byte represents 8 application bytes):
  Addressable:           00
  Partially addressable: 01 02 03 04 05 06 07 
  Heap left redzone:       fa
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  Stack after return:      f5
  Stack use after scope:   f8
  Global redzone:          f9
  Global init order:       f6
  Poisoned by user:        f7
  Container overflow:      fc
  Array cookie:            ac
  Intra object redzone:    bb
  ASan internal:           fe
  Left alloca redzone:     ca
  Right alloca redzone:    cb
==123306==ABORTING

when .zsh_histroy contains following line

: