Login white page

Hi, I’m using wordpress with a childtheme and when i go to login page a blank page appears. This issue happens only with childtheme, not when I use the original theme. I have any problem with wp-login.php page and wp-admin but only with this login page (and registration page) when using childtheme: http://www.offrogratis.it/?ptype=login&page1=sign_in . I checked in childtheme’s functions.php for blank spaces but I’ve found any problem. Thank you for any help in advance.

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