Handle empty points in localizer (#477)

Author: Phil26AT

hloc/localize_sfm.py

@@ -58,6 +58,8 @@ def __init__(self, reconstruction, config=None):
     def localize(self, points2D_all, points2D_idxs, points3D_id, query_camera):
         points2D = points2D_all[points2D_idxs]
         points3D = [self.reconstruction.points3D[j].xyz for j in points3D_id]
+        if points2D.shape[0] == 0:
+            return None
         ret = pycolmap.estimate_and_refine_absolute_pose(
             points2D,
             points3D,