add error checking for non-existent users trying to log in

src/backend/database.py

@@ -1217,10 +1217,13 @@ class Database:
         Returns:
             bool: True if the login was successful, False if not
         """
-        salt = self.query_db(
+        try:
-            "SELECT salt FROM user WHERE username=?", (user,), one=True
+            salt = self.query_db(
-        )[0]
+                "SELECT salt FROM user WHERE username=?", (user,), one=True
-        if salt is None:
+            )[0]
+            if salt is None:
+                return False
+        except TypeError:
             return False
         hashed_password = salt + hashed_password
         password = self.query_db(