Click area of buttons on ProseMirror toolbar is smaller than button

[Atul Varma]

I just noticed that the "click area" of buttons, i.e. the part of the button that actually responds to mouse clicks, isn't actually the same as the visible size of the button. This means that if the user e.g. clicks near the left or right edge of the "P" (add new paragraph) button, instead of adding a new paragraph, the text cursor will disappear from the ProseMirror editor and no new paragraph will be added anywhere, which is really confusing.