Fix MaterialCommand

Signed-off-by: yoyosource <yoyosource@nidido.de>

BauSystem_Main/src/de/steamwar/bausystem/features/util/MaterialCommand.java

@@ -69,7 +69,7 @@ public class MaterialCommand extends SWCommand {
             if (value.isFlammable()) {
                 lore.add(BauSystem.MESSAGE.parse("MATERIAL_FLAMMABLE", p));
             }
-            SWItem swItem = new SWItem(value.isItem() ? value : Material.GHAST_TEAR, "§e" + value.name(), lore, false, clickType -> {});
+            SWItem swItem = new SWItem(value.isItem() || value == Material.AIR ? value : Material.GHAST_TEAR, "§e" + value.name(), lore, false, clickType -> {});
             swListEntries.add(new SWListInv.SWListEntry<>(swItem, value));
         }
         SWListInv<Material> materialSWListInv = new SWListInv<>(p, BauSystem.MESSAGE.parse("MATERIAL_INV_NAME", p), false, swListEntries, (clickType, material) -> {});