fix: don't make path empty when truncating trailing slashes (#38844)

Fixes the following Coverity warning:

*** CID 549779:         Integer handling issues  (INTEGER_OVERFLOW)
/src/nvim/undo.c: 717             in u_get_undo_file_name()
711           dir_name[dir_len] = NUL;
712
713           // Remove trailing pathseps from directory name
714           char *p = &dir_name[dir_len - 1];
715           while (vim_ispathsep(*p)) {
716             *p-- = NUL;
>>>     CID 549779:         Integer handling issues  (INTEGER_OVERFLOW)
>>>     Expression "dir_len--", where "dir_len" is known to be equal to 0, underflows the type of "dir_len--", which is type "size_t".
717             dir_len--;
718           }
719
720           bool has_directory = os_isdir(dir_name);
721           if (!has_directory && *dirp == NUL && !reading) {
722             // Last directory in the list does not exist, create it.

0 files changed, 0 insertions, 0 deletions