Custom Texture Fix

Fix old (before 1.19.3) custom resource packs with a "custom" texture folder.

Thanks to https://bugs.mojang.com/browse/MC-259931?focusedId=1237160&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#comment-1237160 for the solution.

This resource pack will not be updated and should work on higher versions of the game.