fix: crash when backwards is empty

[Bloeckchengrafik]

Fixes a crash when backwards is empty on go-to-defintion:

/usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/16/../../../../include/c++/16/bits/basic_string.h:2409: void std::basic_string<char>::pop_back() [_CharT = char, _Traits = std::char_traits<char>, _Alloc = std::allocator<char>]: Assertion '!empty()' failed.

Thanks for reviewing & maintaining! Awesome work!