Handle empty IO result

src/collectors/container_collector.py

@@ -203,6 +203,10 @@ class ContainerCollector(BaseCollector):
             blkio_stats = stats.get('blkio_stats', {})
             io_service_bytes = blkio_stats.get('io_service_bytes_recursive', [])
             
+            # Handle case where io_service_bytes might be None
+            if io_service_bytes is None:
+                io_service_bytes = []
+            
             read_bytes = 0
             write_bytes = 0