fix: correcting expected matrix type and None comparison

matsciml/datasets/utils.py

@@ -699,7 +699,7 @@ def make_pymatgen_periodic_structure(
             is_frac = True
     else:
         is_frac = not is_cartesian  # TODO this is logically confusing
-    if not lattice:
+    if lattice is None:
         if lat_angles is None or lat_abc is None:
             raise ValueError(
                 "Unable to construct Lattice object without parameters:"
@@ -894,6 +894,10 @@ def calculate_ase_periodic_shifts(
     frac_coords = torch.from_numpy(atoms.get_scaled_positions()).float()
     coords = torch.from_numpy(atoms.positions).float()
 
+    # convert numpy cells to torch in advance for einsum
+    if isinstance(cell, np.ndarray):
+        cell = torch.from_numpy(cell).float()
+
     return_dict = {
         "src_nodes": torch.LongTensor(all_src),
         "dst_nodes": torch.LongTensor(all_dst),