Sync before height command

lib/src/commands.rs

@@ -627,10 +627,13 @@ impl Command for HeightCommand {
     }
 
     fn exec(&self, _args: &[&str], lightclient: &LightClient) -> String {
-        format!("{}",
-            object! {
-                "height" => lightclient.last_scanned_height()
-            }.pretty(2))
+        match lightclient.do_sync(true) {
+            Ok(_) => format!("{}",
+                        object! {
+                            "height" => lightclient.last_scanned_height()
+                        }.pretty(2)),
+            Err(e) => e
+        }
     }
 }