don't run the damage ABM if damage is disabled on the server.

technic/machines/HV/nuclear_reactor.lua

@@ -569,6 +569,10 @@ end
 local assumed_abdomen_offset = vector.new(0, 1, 0)
 local assumed_abdomen_offset_length = vector.length(assumed_abdomen_offset)
 local cache_scaled_shielding = {}
+
+local damage_enabled = minetest.setting_getbool("enable_damage")
+
+if damage_enabled then
 	minetest.register_abm({
 		nodenames = {"group:radioactive"},
 		interval = 1,
@@ -610,6 +614,7 @@ minetest.register_abm({
 			end
 		end,
 	})
+end
 
 -- radioactive materials that can result from destroying a reactor