Merge pull request #45 from roboflow/fix/042_fix_with_nms_when_detections_is_empty

🧪 ready for tests

supervision/detection/core.py

@@ -249,6 +249,9 @@ class Detections:
         Raises:
             AssertionError: If `confidence` is None and class_agnostic is False. If `class_id` is None and class_agnostic is False.
         """
+        if len(self) == 0:
+            return self
+
         assert (
             self.confidence is not None
         ), f"Detections confidence must be given for NMS to be executed."

test/detection/test_utils.py

@@ -11,6 +11,12 @@ from supervision.detection.utils import non_max_suppression
 @pytest.mark.parametrize(
     "predictions, iou_threshold, expected_result, exception",
     [
+        (
+            np.empty(shape=(0, 5)),
+            0.5,
+            np.array([]),
+            DoesNotRaise()
+        ),  # single box with no category
         (
             np.array([
                 [10.0, 10.0, 40.0, 40.0, 0.8]