Explicitly check name to be not None

Author: AFanaei

mypy/semanal.py

@@ -2128,11 +2128,11 @@ def analyze_namedtuple_assign(self, s: AssignmentStmt) -> bool:
                                                                           self.is_func_scope())
         if not is_named_tuple:
             return False
-        if isinstance(s.lvalues[0], MemberExpr):
-            self.fail("NamedTuple type as an attribute is not supported", s.lvalues[0])
+        if isinstance(lvalue, MemberExpr):
+            self.fail("NamedTuple type as an attribute is not supported", lvalue)
             return False
         # Yes, it's a valid namedtuple, but defer if it is not ready.
-        if not info:
+        if not info and name is not None:
             self.mark_incomplete(name, lvalue, becomes_typeinfo=True)
         return True