fix: correctly handle salt=0 in encrypt_cisco_type7

The function `encrypt_cisco_type7` was incorrectly handling the integer `0` as a missing argument because of the thruthiness check (`if not salt:`). This resulted in a random salt being used when the user explicitely requested salt `0`.

The condition has been updated to `if salt is None` to differentiate between a provided `0` and the default `None`.

Author: Mathieu Payrol

netutils/password.py

@@ -292,7 +292,7 @@ def encrypt_cisco_type7(unencrypted_password: str, salt: t.Optional[int] = None)
     if len(unencrypted_password) > ENCRYPT_TYPE7_LENGTH:
         raise ValueError("Password must not exceed 25 characters.")
 
-    if not salt:
+    if salt is None:
         salt = random.randint(0, 15)  # noqa: S311
     # Start building the encrypted password - pre-pend the 2 decimal digit offset.
     encrypted_password = format(salt, "02d")