fix: dynamic unified title

music_kraken/utils/string_processing.py

@@ -16,9 +16,12 @@ def unify(string: str) -> str:
     """
     returns a unified str, to make comparisons easy.
     a unified string has the following attributes:
-     - is lowercase
+    - is lowercase
     """
 
+    if string is None:
+        return None
+
     try:
         string = translit(string, reversed=True)
     except LanguageDetectionError: