First of all, I just realized that you may need a bit of context: I'm sorry, I'm pretty new to contributing.
The "Handling the errors" section in the first chapter of the Tutorial states that calling ssh_get_error() and ssh_get_error_code() with NULL as argument is fine. Looking at the source code, that will make the library segfault, derefencing NULL. The patch rephrases the paragraph, clarifying how to use said functions.
