Remove the sub page when using the form in Special:ListFiles

Follow-up Ie0a2819fdf (c01c4f0) to make I431be530ad (e1284b2)
work again.

Change-Id: Ib81c99940693fd26004682f1f61c8c7e7c42d437
Merge "Remove the sub page when using the form in Special:ListFiles"