Fix tensor creation with empty names crash (#163957)

Partially fixes #148324

Pull Request resolved: https://github.com/pytorch/pytorch/pull/163957
Approved by: https://github.com/malfet, https://github.com/janeyx99

test/test_namedtensor.py

@@ -280,6 +280,11 @@ class TestNamedTensor(TestCase):
         self.assertEqual(named_tensor.diagonal(outdim='E', dim1='B', dim2='D').names,
                          ['A', 'C', 'E'])
 
+    def test_empty_names(self):
+        ref_tensor = torch.tensor([[1, 2, 3, 4], [4, 3, 2, 1]])
+        empty_named_tensor = torch.tensor([[1, 2, 3, 4], [4, 3, 2, 1]], names=[])
+        self.assertEqual(ref_tensor, empty_named_tensor)
+
     def test_max_pooling(self):
         def check_tuple_return(op, inputs, expected_names):
             values, indices = op(*inputs)

torch/csrc/utils/tensor_new.cpp

@@ -1497,7 +1497,7 @@ Tensor tensor_ctor(
         pin_memory);
     auto names = r.toDimnameListOptional(5);
     if (names) {
-      at::namedinference::propagate_names(
+      at::namedinference::propagate_names_if_nonempty(
           new_tensor, *names, /*validate_names=*/true);
     }
     new_tensor.detach_(); // ensure new_tensor a leaf node