Timer input fields are selectable when disabled

[johndoe31415]

When the timer is running, the "end of presentation" and "slide subset" input type="text" fields are both disabled. However, I can still select text within them which leads to a weird/confusing UX. A web search shows that this should not be the case (disabled=true prevents focus) but an attempt of user-select: none did not work, either. Investigate the issue further.