Respect immortal armor group, ensuring objects are not dealt damage

Context: some objects such as chest, frame or sign entities are set to
be immortal, because they are tied to a node and should not be removed
on their own.

However since immortality wasn't respected, it would lead to odd desync
issues between nodes and accompanying entities. An example is a chest
that becomes invisible when struck by lightning or anvil.

mods/CORE/mcl_util/init.lua

@@ -556,6 +556,11 @@ function mcl_util.deal_damage(target, damage, mcl_reason)
 		end
 	end
 
+	local is_immortal = target:get_armor_groups().immortal or 0
+	if is_immortal>0 then
+		return
+	end
+
 	local hp = target:get_hp()
 
 	if hp > 0 then