'mViewportMetrics' can be null here, e.g. while the document is still being loaded. This fixes a crash that happened e.g. when tapping on the screen while document was still being loaded. Change-Id: Ib3f237ecf64c05a5736d97e00b46d0de2ef051a0 Reviewed-on: https://gerrit.libreoffice.org/c/core/+/90048 Tested-by: Jenkins Reviewed-by: Michael Weghorn <m.weghorn@posteo.de>