Fix crash when add_earthkit_attrs=False used in Xarray engine (#696)

* Fix crash when add_earthkit_attrs=False used in Xarray engine

Author: sandorkertesz

src/earthkit/data/utils/xarray/builder.py

@@ -407,7 +407,7 @@ def prepare_tensor(self, ds, dims, name):
                 elif num > 1 or not self.profile.dims.squeeze or d.name in self.profile.dims.ensure_dims:
                     tensor_dims.append(d)
                     tensor_coords[d.key] = vals[d.key]
-                    if d.key in component_vals:
+                    if component_vals and d.key in component_vals:
                         tensor_coords_component[d.key] = component_vals[d.key]
 
                     # check if the dims/coords are consistent with the tensors of

tests/xr_engine/test_xr_engine.py

@@ -542,7 +542,7 @@ def test_xr_engine_single_field():
 
 @pytest.mark.cache
 @pytest.mark.parametrize("add", [False, True])
-def test_xr_engine_add_earthkit_attrs(add):
+def test_xr_engine_add_earthkit_attrs_1(add):
     ds_ek = from_source("url", earthkit_remote_test_data_file("test-data/xr_engine/level/pl.grib"))
     ds_ek = ds_ek[0]
 
@@ -558,3 +558,16 @@ def test_xr_engine_add_earthkit_attrs(add):
         assert "_earthkit" in ds["t"].attrs
     else:
         assert "_earthkit" not in ds["t"].attrs
+
+
+@pytest.mark.cache
+def test_xr_engine_add_earthkit_attrs_2():
+    ds_ek = from_source("url", earthkit_remote_test_data_file("test-data/xr_engine/level/pl.grib"))
+    ds_ek = ds_ek[0]
+
+    ds = ds_ek.to_xarray(
+        add_earthkit_attrs=False,
+    )
+
+    assert ds
+    assert "_earthkit" not in ds["t"].attrs