BookletLayout: Clear currentPageName when removing that page
BookletLayout: Clear currentPageName when removing that page

In Id9cf08677103 we removed a call to selectFirstSelectablePage
which usually ensured currentPageName was updated after removing
a page.

We should set currentPageName to null if is the name of the
page being removed.

Bug: T301256
Change-Id: Ib9b8c47397768e31b31bcc9bfa5959a2da73fef3

wikimedia/oojs-ui,wikimedia/oojs-ui,wikimedia/oojs-ui,wikimedia/oojs-ui