Fix random string generation

Our variable `alphabet` contains 62 alphanumeric symbols + '\0'.
When we use sizeof(alphabet) we will get 63 due to that.
But we want to choose a random numbers from the 62 alphanumeric letters only.

This mistake caused us to have strings with a max length of `length`
instead of the exact length.

When doing https://github.com/profanity-im/profanity/issues/1520
this caused our algo for muc reflection to not catch since we expect the
random ID to be exactly 15 symbols long in `message_is_sent_by_us()`.

0 files changed, 0 insertions, 0 deletions