Webcam inference fix (#202)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Glenn Jocher <glenn.jocher@ultralytics.com>

ultralytics/yolo/v8/segment/predict.py

@@ -3,7 +3,7 @@
 import hydra
 import torch
 
-from ultralytics.yolo.utils import DEFAULT_CONFIG, ops
+from ultralytics.yolo.utils import DEFAULT_CONFIG, ROOT, ops
 from ultralytics.yolo.utils.checks import check_imgsz
 from ultralytics.yolo.utils.plotting import colors, save_one_box
 
@@ -103,6 +103,8 @@ class SegmentationPredictor(DetectionPredictor):
 def predict(cfg):
     cfg.model = cfg.model or "yolov8n-seg.pt"
     cfg.imgsz = check_imgsz(cfg.imgsz, min_dim=2)  # check image size
+    cfg.source = cfg.source if cfg.source is not None else ROOT / "assets"
+
     predictor = SegmentationPredictor(cfg)
     predictor()