fix node-red crash with invalid mqtt birth topic

fixes node-red#3865

Author: Steve-Mcl

packages/node_modules/@node-red/nodes/core/network/10-mqtt.js

@@ -991,14 +991,21 @@ module.exports = function(RED) {
                 }
 
                 if (topicOK) {
-                    node.client.publish(msg.topic, msg.payload, options, function(err) {
-                        done && done(err);
-                        return
-                    });
+                    node.client.publish(msg.topic, msg.payload, options, function (err) {
+                        if (done) {
+                            done(err)
+                        } else {
+                            node.error(err, msg)
+                        }
+                    })
                 } else {
-                    const error = new Error(RED._("mqtt.errors.invalid-topic"));
-                    error.warn = true;
-                    done(error);
+                    const error = new Error(RED._("mqtt.errors.invalid-topic"))
+                    error.warn = true
+                    if (done) {
+                        done(error)
+                    } else {
+                        node.warn(error, msg)
+                    }
                 }
             }
         };