Fix make unrepairable (#25)

Due to a table reference in builtin, modifying the table directly affected other items as well. The function will now copy the values into a new table to replace the table reference.

init.lua

@@ -18,36 +18,39 @@ local hammer_repairable = minetest.settings:get_bool("anvil_hammer_is_repairable
 anvil.make_unrepairable = function(item_name)
 	local item_def = minetest.registered_items[item_name]
 	if item_def then
-		item_def.groups.not_repaired_by_anvil = 1
-		minetest.override_item(item_name, {groups = item_def.groups})
+		-- Drop table reference. Copy other values over.
+		local groups = { not_repaired_by_anvil = 1 }
+		for k, v in pairs(item_def.groups) do groups[k] = v end
+		minetest.override_item(item_name, {groups = groups})
 	end
 end
 
--- make rechargeable technic tools unrepairable
-anvil.make_unrepairable("technic:water_can")
-anvil.make_unrepairable("technic:lava_can")
-anvil.make_unrepairable("technic:flashlight")
-anvil.make_unrepairable("technic:battery")
-anvil.make_unrepairable("technic:vacuum")
-anvil.make_unrepairable("technic:prospector")
-anvil.make_unrepairable("technic:sonic_screwdriver")
-anvil.make_unrepairable("technic:chainsaw")
-anvil.make_unrepairable("technic:laser_mk1")
-anvil.make_unrepairable("technic:laser_mk2")
-anvil.make_unrepairable("technic:laser_mk3")
-anvil.make_unrepairable("technic:mining_drill")
-anvil.make_unrepairable("technic:mining_drill_mk2")
-anvil.make_unrepairable("technic:mining_drill_mk2_1")
-anvil.make_unrepairable("technic:mining_drill_mk2_2")
-anvil.make_unrepairable("technic:mining_drill_mk2_3")
-anvil.make_unrepairable("technic:mining_drill_mk2_4")
-anvil.make_unrepairable("technic:mining_drill_mk3")
-anvil.make_unrepairable("technic:mining_drill_mk3_1")
-anvil.make_unrepairable("technic:mining_drill_mk3_2")
-anvil.make_unrepairable("technic:mining_drill_mk3_3")
-anvil.make_unrepairable("technic:mining_drill_mk3_4")
-anvil.make_unrepairable("technic:mining_drill_mk3_5")
-
+if minetest.get_modpath("technic") then
+	-- make rechargeable technic tools unrepairable
+	anvil.make_unrepairable("technic:water_can")
+	anvil.make_unrepairable("technic:lava_can")
+	anvil.make_unrepairable("technic:flashlight")
+	anvil.make_unrepairable("technic:battery")
+	anvil.make_unrepairable("technic:vacuum")
+	anvil.make_unrepairable("technic:prospector")
+	anvil.make_unrepairable("technic:sonic_screwdriver")
+	anvil.make_unrepairable("technic:chainsaw")
+	anvil.make_unrepairable("technic:laser_mk1")
+	anvil.make_unrepairable("technic:laser_mk2")
+	anvil.make_unrepairable("technic:laser_mk3")
+	anvil.make_unrepairable("technic:mining_drill")
+	anvil.make_unrepairable("technic:mining_drill_mk2")
+	anvil.make_unrepairable("technic:mining_drill_mk2_1")
+	anvil.make_unrepairable("technic:mining_drill_mk2_2")
+	anvil.make_unrepairable("technic:mining_drill_mk2_3")
+	anvil.make_unrepairable("technic:mining_drill_mk2_4")
+	anvil.make_unrepairable("technic:mining_drill_mk3")
+	anvil.make_unrepairable("technic:mining_drill_mk3_1")
+	anvil.make_unrepairable("technic:mining_drill_mk3_2")
+	anvil.make_unrepairable("technic:mining_drill_mk3_3")
+	anvil.make_unrepairable("technic:mining_drill_mk3_4")
+	anvil.make_unrepairable("technic:mining_drill_mk3_5")
+end
 
 local S = minetest.get_translator(minetest.get_current_modname())