What is the background on your login page? When that page is white, that is probably the white space you'll see.
You should be able to add a class to your page in "Edit Page" (right click on the gray menu area and select properties). Or, if you don't want to start up gulp or grunt, you could test it just by typing: 'background-color: YourShadeOfGray;' in "Style" and then run the application.
Good luck!
A class or indeed the css in style on the page will solve the issue