Check if string_names is None before returning string_names (#1708)

* Check if string is None before using string_names

* Add test asserting None string_names returns an empty list

* Remove whitespace to pass flake8

* Add name to authors.txt

Co-authored-by: Leo Ryu <leo@episci.com>

jedi/inference/value/module.py

@@ -179,6 +179,9 @@ class ModuleValue(ModuleMixin, TreeValue):
         return self._is_package
 
     def py__package__(self):
+        if self.string_names is None:
+            return []
+
         if self._is_package:
             return self.string_names
         return self.string_names[:-1]