Handle cases where the field isn't present in network.json for backwards compatibility.

src/rust/lqos_config/src/network_json/mod.rs

@@ -48,7 +48,7 @@ impl NetworkJsonNode {
       rtts: self.rtts.iter().map(|n| *n as f32 / 100.0).collect(),
       parents: self.parents.clone(),
       immediate_parent: self.immediate_parent,
-      node_type: String::new(),
+      node_type: None,
     }
   }
 }
@@ -72,7 +72,7 @@ pub struct NetworkJsonTransport {
   pub immediate_parent: Option<usize>,
   /// The type of node (site, ap, etc.)
   #[serde(rename = "type")]
-  pub node_type: String,
+  pub node_type: Option<String>,
 }
 
 /// Holder for the network.json representation.

src/rust/lqosd/src/shaped_devices_tracker/mod.rs

@@ -96,7 +96,7 @@ pub fn get_top_n_root_queues(n_queues: usize) -> BusResponse {
           rtts: Vec::new(),
           parents: Vec::new(),
           immediate_parent: None,
-          node_type: String::new(),
+          node_type: None,
         },
       ));
     }