Problem Details:
well as title said, I found some blank beatmap which shouldn't be on website (failed , or something?)

How to replicate:
Simply search with 'Halozy' or 'Genryuu Kaiko' (only for this case) on website with 'All rank status'

Video or screenshot showing the problem:

osu! version: 20150213.1cuttingedge

They are deleted maps
Maybe deleted maps are still in the system?

Confirmed.

Searched Halozy and there were missing maps when selecting the All subcategory.

Yeah, seems to be fixed. I was just wondering about this a couple days ago.

ah you're right