Fixing an npe

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

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

@@ -80,6 +80,7 @@ class GUI {
         SWInventory inv = new SWInventory(p, 9, schem.getSchemName() + " entfernen");
         inv.setItem(0, SWItem.getDye(1), (byte) 1, "§eZugriff entfernen", click -> {
             SchematicMember member = SchematicMember.getSchemMemberFromDB(schem.getSchemName(), schem.getSchemOwner(), SteamwarUser.get(p.getUniqueId()).getId());
+            if(member != null)
                 member.remove();
             p.sendMessage(SchematicSystem.PREFIX + "Zugriff zu Schematic §e" + schem.getSchemName() + " §7entfernt");
             p.closeInventory();