log: Fix crash in `cr_log_info()` on empty string
log: Fix crash in `cr_log_info()` on empty string

Fixes #311.

The issue was caused by an unchecked dereferencing of the first token
returned by `strtok_r()`, which is NULL if the message is empty.

Now the `normal_log_message()` function does an early return if the
messages is empty, instead of trying to extract tokens.

Snaipe/Criterion,offa/Criterion,offa/Criterion,offa/Criterion,Snaipe/Criterion,offa/Criterion,Snaipe/Criterion,Snaipe/Criterion,Snaipe/Criterion,offa/Criterion