Improve guarding

Author: bouwew

plugwise_usb/nodes/node.py

@@ -504,7 +504,7 @@ async def update_node_details(
                 model_info = model_info.split(" ")
                 self._node_info.model = model_info[0]
                 # Handle + devices
-                if "+" in model_info[1]:
+                if len(model_info) > 1 and "+" in model_info[1]:
                     self._node_info.model = model_info[0] = model_info[0:1]
                     model_info.pop(1)