After adding an svg icon and menu text with space (2 words) in categories menu li height is incorrect. If we delete icon or delete second word that problem is gone.
You need to open your SVG icons file with some editor like Sublime Text or default system text editor and add width=”31″ height=”40″ attributes to your <svg> tag like it is shown: http://prntscr.com/m4n0qw
Then you will need to re-upload your icons in WordPress Dashboard.