fix table generation

Author: T4rk1n

dash/development/_py_prop_typing.py

@@ -100,12 +100,12 @@ def type_handler(*_):
 
 
 def _get_literal_value(value):
-    if value is None:
-        return "None"
-
     if isinstance(value, str):
         value = json.loads(value.replace("'", '"'))
 
+    if value is None:
+        return "None"
+
     if isinstance(value, bool):
         return str(value)