A couple of fixes

In function get_command:
1. Open database first, then check for errors, removing the need for file_exists.
2. Add label "success", which closes the file stream and then returns.
In function store_special_variables:
1. Assert var_LL == NULL, instead of creating a if-else branch. (the program will crash automatically if the assertion is not true)
dictionary.c:
1. Make functions parse_args and is_there_enough_args static, as they are not used outside the file.
2. Make function is_there_enough_args inline, as it is just a one line check.
3. Remove file_exists, it is no longer needed.