Fix Illegal argument exception

Signed-off-by: Lixfel <agga-games@gmx.de>

SchematicSystem_Main/src/de/steamwar/schematicsystem/commands/GUI.java

@@ -207,8 +207,13 @@ class GUI {
             Material m;
             if (schem.getItem().isEmpty())
                 m = SWItem.getMaterial("CAULDRON_ITEM");
-            else
-                m = SWItem.getMaterial(schem.getItem());
+            else{
+                try{
+                    m = SWItem.getMaterial(schem.getItem());
+                }catch(IllegalArgumentException e){
+                    m = SWItem.getMaterial("CAULDRON_ITEM");
+                }
+            }
 
             SWItem item = new SWItem(m, "§e" + schem.getSchemName(), Collections.singletonList("§7" + schem.getSchemType().name()), !schem.getSchemType().writeable(), click -> {});
             if(schem.getRank() > 0)