Fix a few errors exposed by difficult setting.

corn.lua

@@ -325,7 +325,7 @@ crops.corn_die = function(pos)
 end
 
 local properties = {
-	wither = crops.corn_die,
+	die = crops.corn_die,
 	waterstart = 40,
 	wateruse = 1,
 	night = 5,

init.lua

@@ -348,7 +348,7 @@ minetest.register_abm({
 
 		-- is it dead?
 		if damage >= 100 then
-			plant.properties.wither(pos)
+			plant.properties.die(pos)
 		end
 	end
 })

melon.lua

@@ -225,7 +225,7 @@ crops.melon_die = function(pos)
 end
 
 local properties = {
-	wither = crops.melon_die,
+	die = crops.melon_die,
 	waterstart = 20,
 	wateruse = 1,
 	night = 5,

polebean.lua

@@ -276,13 +276,13 @@ minetest.register_abm({
 })
 
 crops.beanpole_die = function(pos)
-	minetest.set_node(pos, { name = "crops:beanpole_base_6" })
+	minetest.set_node(pos, { name = "crops:beanpole_plant_base_6" })
 	local above = {x = pos.x, y = pos.y + 1, z = pos.z}
 	minetest.set_node(above, { name = "crops:beanpole_plant_top_4" })
 end
 
 local properties = {
-	wither = crops.beanpole_die,
+	die = crops.beanpole_die,
 	waterstart = 30,
 	wateruse = 1,
 	night = 5,

potato.lua

@@ -172,7 +172,7 @@ crops.potato_die = function(pos)
 end
 
 local properties = {
-	wither = crops.potato_die,
+	die = crops.potato_die,
 	waterstart = 30,
 	wateruse = 1,
 	night = 5,

tomato.lua

@@ -173,7 +173,7 @@ crops.tomato_die = function(pos)
 end
 
 local properties = {
-	wither = crops.tomato_die,
+	die = crops.tomato_die,
 	waterstart = 19,
 	wateruse = 1,
 	night = 5,