Spreadsheet lookup by empty cell as a key

I know how to lookup last non-empty value in a row using =LOOKUP("X";$B2:$E2;$B1:$E1)

But if I try to use an empty cell as a key, it causes an #N\A as a result.

How can I get "5 Jan" as a result in this example? I need to get date that matches up last empty cell in a row.