traceo-sdk-browser. Browser cancels XMLHttpRequest.send(...) on window.beforeunload event

[AlexeyBarsuk]

When refreshing or leaving window the window.beforeunload event if fired. This leads Performance.batch object to call flush method, that calls XMLHttpRequest.send. As browser closes (or leaving) the window, this request is being cancelled.
In this situation Firefox throws error "Error: [Traceo SDK] Cannot send data to Traceo Platform. Make sure the application is running. Caused by: TypeError: NetworkError when attempting to fetch resource." that is being caught by traceo and sent to traceo server.
Google Chrome just silently cancels request with no errors emitted.