crash if compliing in debug mode, everything is ok if in release mode

[feixyz10]

In CMakeLists.txt add set(CMAKE_BUILD_TYPE "Debug") after line 10, then run the excutable. The program crashed with following error message:

Assertion failed: (encoder_.size() != decoder_.size() && "Encoder and decoder must be of equal length; maybe you had duplicate token indices in your encoder?"), function tiktoken, file tiktoken.h, line 139.

My running env: macbook pro with MI chip, clang version 15.0.0.