raise in plot if slices results in a dataset which is not 2D

dkist/dataset/tiled_dataset.py

@@ -227,6 +227,11 @@ def plot(self, slice_index, share_zscale=False, figure=None, swap_tile_limits: L
             figure = plt.gcf()
 
         sliced_dataset = self.slice_tiles[slice_index]
+        if (nd_sliced := len(sliced_dataset.flat[0].shape)) != 2:
+            raise ValueError(
+                f"Applying slice '{slice_index}' to this dataset resulted in a {nd_sliced} "
+                "dimensional dataset, you should pass a slice which results in a 2D dataset for each tile."
+            )
         dataset_ncols, dataset_nrows = sliced_dataset.shape
         gridspec = GridSpec(nrows=dataset_nrows, ncols=dataset_ncols, figure=figure)
         for col in range(dataset_ncols):