bugfix: crash unless first mouse click on settings

0087-on_slider

@@ -1,4 +1,5 @@
 on_slider = function(slider, x,y)
+	if slider.x0 == nil then return end  -- slider uninitialized
 	if x < slider.x0-slider.w/2 or x > slider.x1+slider.w/2 then return end
 	if y < slider.y0-slider.h/2 or y > slider.y0+slider.h/2 then return end
 	return true

0093-on_area

@@ -1,4 +1,5 @@
 on_area = function(s, x,y)
+	if s.x == nil then return end
 	if x < s.x then return end
 	if x > s.x+s.w then return end
 	if y < s.y then return end