Return None instead of raising an error when converting path objects

openlp/core/common/path.py

@@ -206,7 +206,8 @@ def str_to_path(string):
     :rtype: openlp.core.common.path.Path | None
     """
     if not isinstance(string, str):
-        raise TypeError('parameter \'string\' must be of type str')
+        log.debug('parameter \'string\' must be of type str, got {} which is a {} instead'.format(string, type(string)))
+        return None
     if string == '':
         return None
     return Path(string)

tests/functional/openlp_core/common/test_path.py

@@ -271,13 +271,12 @@ class TestPath(TestCase):
 
     def test_str_to_path_type_error(self):
         """
-        Test that `str_to_path` raises a type error when called with an invalid type
+        Test that `str_to_path` returns None if called with invalid information
         """
         # GIVEN: The `str_to_path` function
         # WHEN: Calling `str_to_path` with an invalid Type
-        # THEN: A TypeError should have been raised
-        with self.assertRaises(TypeError):
-            str_to_path(Path())
+        # THEN: None is returned
+        assert str_to_path(Path()) is None
 
     def test_str_to_path_empty_str(self):
         """