IndexDefect when using searchIndex.search about cello HOT 2 OPEN

BenjaminLee@mbp ~/r/playground [1]> nim r monomerize.nim                        (viroid-search) 
Hint: used config file '/usr/local/Cellar/nim/1.6.0/nim/config/nim.cfg' [Conf]
Hint: used config file '/usr/local/Cellar/nim/1.6.0/nim/config/config.nims' [Conf]
....................................................................................................
CC: monomerize.nim
Hint:  [Link]
Hint: gc: refc; opt: none (DEBUG BUILD, `-d:release` generates faster code)
58492 lines; 1.388s; 93.918MiB peakmem; proj: /Users/BenjaminLee/research/playground/monomerize.nim; out: /Users/BenjaminLee/.cache/nim/monomerize_d/monomerize_4651918B165140654B6F77303C1F7E8C0EB6DBDA [SuccessX]
Hint: /Users/BenjaminLee/.cache/nim/monomerize_d/monomerize_4651918B165140654B6F77303C1F7E8C0EB6DBDA  [Exec]
@[67, 237, 111, 149, 114, 284, 120, 42, 122, 0, 312, 90, 230, 260, 330]
/Users/BenjaminLee/research/playground/monomerize.nim(12) monomerize
/Users/BenjaminLee/.nimble/pkgs/cello-0.3.0/cello.nim(802) search
/Users/BenjaminLee/.nimble/pkgs/cello-0.3.0/cello.nim(795) search
/Users/BenjaminLee/.nimble/pkgs/cello-0.3.0/cello.nim(435) rank
/Users/BenjaminLee/.nimble/pkgs/cello-0.3.0/cello.nim(434) rank
/Users/BenjaminLee/.nimble/pkgs/cello-0.3.0/cello.nim(320) rank
/usr/local/Cellar/nim/1.6.0/nim/lib/system/fatal.nim(53) sysFatal
Error: unhandled exception: index 4 not in 0 .. 3 [IndexDefect]
Error: execution of an external program failed: '/Users/BenjaminLee/.cache/nim/monomerize_d/monomerize_4651918B165140654B6F77303C1F7E8C0EB6DBDA '