Fix case of dims = [None, None, ...]

The only case where dims=[None, ...] is when the user has passed dims=None. Since the user passed dims=None,
they shouldn't be expecting any coords to match that dimension. Thus we don't need to try to add any
more coords to the model.

pymc/data.py

@@ -459,7 +459,7 @@ def Data(
         xshape = x.shape
         # Register new dimension lengths
         for d, dname in enumerate(new_dims):
-            if dname not in model.dim_lengths:
+            if dname not in model.dim_lengths and dname is not None:
                 model.add_coord(
                     name=dname,
                     # Note: Coordinate values can't be taken from