fix: 🐛 Fix writing bugs

Tested via the cellmap-segmentation-challenge repo.

src/cellmap_data/dataset_writer.py

@@ -381,7 +381,7 @@ def __setitem__(
                 for c, label in enumerate(self.classes):
                     self.target_array_writers[array_name][label][
                         self._current_center
-                    ] = array[c]
+                    ] = array[:, c, ...]
 
     def __repr__(self) -> str:
         """Returns a string representation of the dataset."""

src/cellmap_data/image.py

@@ -933,7 +933,10 @@ def __setitem__(
                     f"Writing to center {center} in image {self.path} failed. Coordinates: are not all within the image's bounds. Will drop out of bounds data."
                 )
                 # Crop data to match the number of coordinates matched in the image
-                slices = [slice(None, len(coord)) for coord in coords.values()]
+                slices = []
+                for coord in coords.values():
+                    if len(coord) > 1:
+                        slices.append(slice(None, len(coord)))
                 data = data[*slices]
                 self.array.loc[coords] = data