You can set a link to the login form instead of using the login button. The login button works only if it is on the same page as the blog widget (and it is optional, so it can be removed), but you can create a link to the login page as followed:
Click on the “show all“ button on the menu of your blog, or reach the main page of your blog. Change the URL in the address bar and replace the word “all” after the slash at the end by “login”. This URL will lead to the login page of your blog.