Look for places we are assigning to the same variable twice
in succession, which means we can simplify that to a single assign

Change-Id: I499d20e28f5595e81e927bef8e1bf364eea8ba91
Reviewed-on: https://gerrit.libreoffice.org/70531
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>