This evidently happens sometimes, but when it does it it's
impossible to reproduce... Let's use SAL_WARN for now.

Change-Id: Id724fd52060bfae45f9eeb16163ddfc94e53af03
Reviewed-on: https://gerrit.libreoffice.org/64447
Tested-by: Jenkins
Reviewed-by: Michael Stahl <Michael.Stahl@cib.de>
(cherry picked from commit d1138d72)
Reviewed-on: https://gerrit.libreoffice.org/64451