Fix inference YOLO model on grayscale images (#9267)

Author: azhavoro

changelog.d/20250401_145904_andrey_fix_yolo_model.md

@@ -0,0 +1,4 @@
+### Fixed
+
+- Fixed inference with the YOLOv7 model on grayscale images
+  (<https://github.com/cvat-ai/cvat/pull/9267>)

serverless/onnx/WongKinYiu/yolov7/nuclio/main.py

@@ -29,7 +29,7 @@ def handler(context, event):
     data = event.body
     buf = io.BytesIO(base64.b64decode(data["image"]))
     threshold = float(data.get("threshold", 0.5))
-    image = Image.open(buf)
+    image = Image.open(buf).convert("RGB")
 
     results = context.user_data.model.infer(image, threshold)