ui.move refuses a coordinate that isn't finite once narrowed to a
pointer position; ui.click {x, y} and ui.drag did not, so 1e39 became
an infinite position and was queued. With debug assertions on, the
next idle frame panicked in emath comparing NaN vectors.
Both now refuse such a coordinate with an error, as ui.move does, and
ui.drag also refuses ends too far apart for the way between them to
stay finite.
Adds click_and_drag_refuse_coordinates_that_overflow_like_move in
tests/control.rs, which panics before this change.
Marco Arnulfo
595026aa69