CERTUS IconSet does not default to DULL properly for Double Plate for ingot

### Checked for existing issues - [x] I have checked for existing issues, and have found none. ### Tested latest version - [x] I have checked that this occurs on the latest version. ### GregTech CEu Version v7.5.3 ### Minecraft Version 1.20.1 Forge ### Recipe Viewer Installed EMI ### Environment Singleplayer ### Cross-Mod Interaction No ### Other Installed Mods JEI, EMI, AE2, Botania, ExtraBotany, Jade. In a dev environment based on the Addon Template. ### Expected Behavior Double Plate for material should default to the DULL IconSet in the absence of one in the CERTUS IconSet. ### Actual Behavior Double Plates registered under CERTUS IconSet will generate without textures at all. <img width="658" height="287" alt="Image" src="https://github.com/user-attachments/assets/5f713854-e76a-48f4-9877-cdcfa5f98fb2" /> ### Steps to Reproduce Register a material with the IconSet CERTUS and a type of .ingot(). An example of a broken textured double plate can be replicated with ```java public static void register() { Material TEST = new Material.Builder( MODID.id("test")) .ingot().color(0x000000).color2(0x000000).iconSet(GTMaterialIconSet.CERTUS) .flags(MaterialFlags.GENERATE_PLATE) .buildAndRegister(); }; ``` ### Additional Information _No response_