Several query vars only accept a scalar value and pass the value through functions that assume a scalar value. Adding extra guard conditions to the types of query vars doesn't affect their functionality but does remove PHP notices and warnings that can otherwise be generated when a non-scalar value such as an array is present in a query var.
Props juliobox, xknown, SergeyBiryukov, dave1010, nacin, tellyworth, dd32, audrasjb, johnregan3
Fixes#17737
git-svn-id: https://develop.svn.wordpress.org/trunk@53891 602fd350-edb4-49c9-b593-d223f7449a82