Do not crash with tenplus1's hopper mod

There are multiple hopper mods and not all of them support the set_extra_container_info function,
so the mod crashes now if it is used together with an incompatible hopper mod.

To prevent the crash, execute the code for hopper compatibility if hopper and hopper.set_extra_container_info exist and not if a mod named hopper is installed.

init.lua

@@ -647,7 +647,7 @@ minetest.register_alias("connected_chests:chest_locked_left",
 minetest.register_alias("connected_chests:chest_locked_right",
 	"default:chest_locked_connected_right")
 
-if minetest.get_modpath("hopper") then
+if minetest.global_exists("hopper") and hopper.set_extra_container_info then
 	local function get_inventory(chest_right_pos)
 		local node_right = minetest.get_node(chest_right_pos)
 		if node_right.param2 > 3 then