Expected behavior

Second click on left hamburger button should hide the sidenav and return the mail content color to the original.

Actual behavior

Sidenav under fixed navbar: Left hamburger icon opens a sidenav, but stays visible and allows multiple clicks, which doesn't toggle the sidenav as it should, but instead shows it again and again, each time dimming the main contents more and more, until it's completely black.

Resources (screenshots, code snippets etc.)