Fix errors around docs of namespace packages, fixes #1890, fixes #1822

jedi/inference/names.py

@@ -248,7 +248,7 @@ class ValueNameMixin:
 
     def get_defining_qualified_value(self):
         context = self.parent_context
-        if context.is_module() or context.is_class():
+        if context is not None and (context.is_module() or context.is_class()):
             return self.parent_context.get_value()  # Might be None
         return None
 

test/test_inference/test_implicit_namespace_package.py

@@ -43,6 +43,9 @@ def test_implicit_namespace_package(Script):
         solution = "foo = '%s'" % solution
         assert completion.description == solution
 
+    c, = script_with_path('import pkg').complete()
+    assert c.docstring() == ""
+
 
 def test_implicit_nested_namespace_package(Script):
     code = 'from implicit_nested_namespaces.namespace.pkg.module import CONST'