fix crash on balrog dead if not enabled tnt explosion

* closes https://codeberg.org/minenux/minetest-mod-mobs_balrog/issues/4
* backported upstream commit bf4b9521cd

minetest.conf

@@ -4,6 +4,7 @@
 
 [subnasa-player-server]
 enable_pvp = true
+enable_tnt = true
 creative_mode = false
 enable_damage = true
 default_privs = interact, shout

mods/mobs_jam/balrog.lua

@@ -117,6 +117,7 @@ if (PATH_FINDER == nil) then
 	PATH_FINDER = 1
 end
 
+local enable_tnt = minetest.settings:get_bool("enable_tnt")
 
 local spawn_nodes = {"group:stone"}
 if minetest.get_modpath("nether") then 
@@ -206,15 +207,18 @@ mobs:register_mob("mobs_jam:balrog", {
 				texture = "fire_basic_flame.png",
 				collisiondetection = true,
 			})
-			tnt.boom(pos, {
-				name = "Balrog's Blast",
-				radius = 14,
-				damage_radius = 50,
-				disable_drops = true,
-				ignore_protection = false,
-				ignore_on_blast = false,
-				tiles = {""},
-			})
+			-- Default to enabled when in singleplayer
+			if enable_tnt then
+				tnt.boom(pos, {
+					name = "Balrog's Blast",
+					radius = 14,
+					damage_radius = 50,
+					disable_drops = true,
+					ignore_protection = false,
+					ignore_on_blast = false,
+					tiles = {""},
+				})
+			end
 		end)
 	end,
 })