script/expect-post-runner.sh: Don't error out if UART plans don't exist

Handle the case when `$WORKSPACE/artefacts/debug/run/uart*` doesn't expand
to any file(s).

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>
Change-Id: I44001f90b45cbbd0572fb073a1db344dc35a50ce
1 file changed