ipneigh: handle missing mac from neighbor entry

src/capport/utils/ipneigh.py

@@ -54,6 +54,8 @@ class NeighborController:
         if neigh is None:
             return None
         mac = neigh.get_attr(neigh.name2nla('lladdr'))
+        if mac is None:
+            return None
         return cptypes.MacAddress.parse(mac)
 
     async def get_route(