fix sampling points (#218)

pcdet/datasets/processor/data_processor.py

@@ -89,9 +89,14 @@ class DataProcessor(object):
             far_idxs_choice = np.where(pts_near_flag == 0)[0]
             near_idxs = np.where(pts_near_flag == 1)[0]
             near_idxs_choice = np.random.choice(near_idxs, num_points - len(far_idxs_choice), replace=False)
-
+            choice = []
+            if num_points > len(far_idxs_choice):
+                near_idxs_choice = np.random.choice(near_idxs, num_points - len(far_idxs_choice), replace=False)
                 choice = np.concatenate((near_idxs_choice, far_idxs_choice), axis=0) \
                     if len(far_idxs_choice) > 0 else near_idxs_choice
+            else: 
+                choice = np.arange(0, len(points), dtype=np.int32)
+                choice = np.random.choice(choice, num_points, replace=False)
             np.random.shuffle(choice)
         else:
             choice = np.arange(0, len(points), dtype=np.int32)