Allow TensorRT inference without metadata (#10152)

Co-authored-by: Glenn Jocher <glenn.jocher@ultralytics.com>

ultralytics/nn/autobackend.py

@@ -234,8 +234,11 @@ class AutoBackend(nn.Module):
             logger = trt.Logger(trt.Logger.INFO)
             # Read file
             with open(w, "rb") as f, trt.Runtime(logger) as runtime:
+                try:
                     meta_len = int.from_bytes(f.read(4), byteorder="little")  # read metadata length
                     metadata = json.loads(f.read(meta_len).decode("utf-8"))  # read metadata
+                except UnicodeDecodeError:
+                    f.seek(0)  # engine file may lack embedded Ultralytics metadata
                 model = runtime.deserialize_cuda_engine(f.read())  # read engine
 
             # Model context