fix to_scalar_or_list when v.ndim == 0 (#1444)

* fix to_scalar_or_list when v.ndim == 0
* add ndim=0 testcase to protect from regressions

_plotly_utils/basevalidators.py

@@ -55,6 +55,8 @@ def to_scalar_or_list(v):
     if isinstance(v, (list, tuple)):
         return [to_scalar_or_list(e) for e in v]
     elif np and isinstance(v, np.ndarray):
+        if v.ndim == 0:
+            return v.item()
         return [to_scalar_or_list(e) for e in v]
     elif pd and isinstance(v, (pd.Series, pd.Index)):
         return [to_scalar_or_list(e) for e in v]

_plotly_utils/tests/validators/test_dataarray_validator.py

@@ -14,7 +14,7 @@ def validator():
 # -----
 # ### Acceptance ###
 @pytest.mark.parametrize('val', [
-    [], [1], [''], (), ('Hello, ',  'world!'), ['A', 1, 'B', 0, 'C']
+    [], [1], [''], (), ('Hello, ',  'world!'), ['A', 1, 'B', 0, 'C'], [np.array(1), np.array(2)]
 ])
 def test_validator_acceptance_simple(val, validator):
     coerce_val = validator.validate_coerce(val)