Fix radiation protection when armor group is not set (#509)

coil

2019-12-30 da95be53ec5703e808233d7b45fc42fb500863dd

 technic/machines/LV/extractor.lua

@@ -4,7 +4,7 @@
minetest.register_craft({
   output = 'technic:lv_extractor',
   recipe = {
      {'technic:treetap', 'technic:motor',          'technic:treetap'},
      {'technic:treetap', 'basic_materials:motor',          'technic:treetap'},
      {'technic:treetap', 'technic:machine_casing', 'technic:treetap'},
      {'',                'technic:lv_cable',       ''},
   }