We ignore clicks until we have touch data because we can't detect where the finger is and thus don't know which software button was pressed. In the clickfinger method, we should let those button events through because the chance of having two fingers on the touchpad without touch data is almost nil, but some devices like the Logitech T650 can be really easy to click without touching the surface.
Author: Peter Hutterer <firstname.lastname@example.org>
Date: Fri Apr 24 12:25:50 2015 +1000
touchpad: allow BTN_LEFT in clickfinger mode without touches