Avoid falling nodes eating digger heads (#94)

If the interval of the digtron is too short (e.g. 1s) while the falling time of nodes in front of the digtron is too long, digtrons may run into them. Previously, this would result in falling nodes destroying the digger head. With this change, the digtron absorbs the falling node and puts it into its inventory.

util.lua

@@ -337,6 +337,14 @@ digtron.damage_creatures = function(player, source_pos, target_pos, amount, item
 						table.insert(items_dropped, lua_entity.itemstring)
 						lua_entity.itemstring = ""
 						obj:remove()
+					elseif lua_entity.name == "__builtin:falling_node" then
+						-- Eat all falling nodes in front of the digtron
+						-- to avoid them eating away our digger heads
+						local drops = minetest.get_node_drops(lua_entity.node, "")
+						for _, item in pairs(drops) do
+							table.insert(items_dropped, item)
+						end
+						obj:remove()
 					else
 						if obj.add_velocity ~= nil then
 							obj:add_velocity(velocity)