Mine turtle: fix refuel

turtles/mine.lua

@@ -116,7 +116,7 @@ function refuel_turtle()
         return false
     end
 
-    go_to(DROP_POINT_H, DROP_POINT_D, DROP_POINT_S)
+    go_to(FUEL_POINT_H, FUEL_POINT_D, FUEL_POINT_S)
     while turtle.getFuelLevel() < FUEL_EXPECTATION do
         local rc, desc = turtle.suckUp()
         if not rc then
@@ -195,8 +195,8 @@ end
 function main()
     if turtle.getFuelLevel() < FUEL_LOW then
         refuel_turtle()
-    else
-        print("NO FUEL AT ALL.")
+    elseif turtle.getFuelLevel() < distance_to_refuel() then
+        print("Not enough fuel to begin with.")
         return
     end