Modify Trie code to avoid a mypy error

cursor is a dict, cursor.get(.., None) returns another dict or None
mypy is being confused as the variable is overwritten, use another
temp variable to handle the case where letter is not in the cursor dict

src/e3/collection/trie.py

@@ -100,8 +100,10 @@ def match(self, word: str, delimiter: str | None = None) -> bool:
             if self.END_MARKER in cursor and (not delimiter or letter in delimiter):
                 return True
             else:
-                cursor = cursor.get(letter, None)
-                if cursor is None:
+                new_cursor = cursor.get(letter, None)
+                if new_cursor is None:
                     return False
+                else:
+                    cursor = new_cursor
 
         return self.END_MARKER in cursor