Sema: handle typo correction with ARC'ed objc properties

We would previously assert in findCapturingExpr when performing a typo
correction resulting in an assignment of an ObjC property with a strong lifetype
specifier due to the expression not being rooted in the file (invalid SLoc)
during the retain cycle check on the typo-corrected expression.  Handle the
expression type appropriately during the TreeTransform to ensure that we have a
source location associated with the expression.

Fixes PR26486.

llvm-svn: 260016