如何确保在加载数据之前我不会访问数据？

I´m new at programming and I my code gets the error: fatal error: unexpectedly found nil while unwrapping an Optional value2017-10-27 16:06:16.755817+0200 Inspireme1.0[836:85307] fatal error: unexpectedly found nil while unwrapping an Optional value(lldb) I´m new at programming and I my code gets the e