satisfy flake8 for pointset.py and catch centroids with no points

siibra/locations/pointset.py

@@ -51,7 +51,8 @@ def from_points(points: List["point.Point"], newlabels: List[Union[int, float, t
     PointSet
     """
     if len(points) == 0:
-        raise EmptyPointSetError(f"Cannot create a PointSet without any coordinates.")
+        raise EmptyPointSetError("Cannot create a PointSet without any points.")
+
     spaces = {p.space for p in points}
     assert len(spaces) == 1, f"PointSet can only be constructed with points from the same space.\n{spaces}"
     coords, sigmas, labels = zip(*((p.coordinate, p.sigma, p.label) for p in points))

siibra/volumes/parcellationmap.py

@@ -618,7 +618,10 @@ def compute_centroids(self, split_components: bool = True, **fetch_kwargs) -> Di
                 space=self.space,
                 split_components=split_components,
             )
-            centroids[regionname] = pointset.from_points([c.centroid for c in props])
+            try:
+                centroids[regionname] = pointset.from_points([c.centroid for c in props])
+            except exceptions.EmptyPointSetError:
+                centroids[regionname] = None
         return centroids
 
     def get_resampled_template(self, **fetch_kwargs) -> _volume.Volume: