Ignore super calls when super class cannot be inferred

jedi/plugins/stdlib.py

@@ -243,6 +243,9 @@ def builtins_super(types, objects, context):
     if isinstance(context, FunctionExecutionContext):
         if isinstance(context.var_args, InstanceArguments):
             su = context.var_args.instance.py__class__().py__bases__()
+            # If super class cannot be infered
+            if len(su) == 0:
+                return NO_CONTEXTS
             return su[0].infer().execute_evaluated()
 
     return NO_CONTEXTS

test/completion/stdlib.py

@@ -276,3 +276,17 @@ qsplit = shlex.split("foo, ferwerwerw werw werw e")
 for part in qsplit:
     #? str()
     part
+
+# -----------------
+# Unknown metaclass
+# -----------------
+
+# Github issue 1321
+class Meta(object):
+    pass
+
+class Test(metaclass=Meta):
+    def test_function(self):
+        result = super(Test, self).test_function()
+        #? []
+        result.