[openthermgateway] transition bridge state via offline to online (#12744)

Signed-off-by: Andrew Fiddian-Green <software@whitebear.ch>

bundles/org.openhab.binding.openthermgateway/src/main/java/org/openhab/binding/openthermgateway/handler/OpenThermGatewayHandler.java

@@ -237,13 +237,14 @@ public class OpenThermGatewayHandler extends BaseBridgeHandler implements OpenTh
     }
 
     private void disconnect() {
-        @Nullable
-        OpenThermGatewayConnector conn = connector;
+        updateStatus(ThingStatus.OFFLINE);
 
         autoReconnect = false;
 
         cancelAutoReconnect();
 
+        @Nullable
+        OpenThermGatewayConnector conn = connector;
         if (conn != null) {
             conn.stop();
             connector = null;