[3.14] gh-142433: Move deref to below the error when checking for laststring (GH-142402) (#142524)

gh-142433: Move deref to below the error when checking for laststring (GH-142402)

Move deref of laststring to below the error checking so the deref
is applied after the object in strings is replaced.
(cherry picked from commit 785268fdceb0d0fe217aed1d6e43e0231c0e50c3)

Co-authored-by: AZero13 <gfunni234@gmail.com>