getPropertyValue("Surround") for a non-inserted frame can throw, but
hasPropertyValue("Surround") still returns true. So fix the regression
by just catching the exception, assuming that in that case no increased
spacing is needed.

Change-Id: I49a78ce8d41b4e1cc7d23721d5dc70f7550c94af
Reviewed-on: https://gerrit.libreoffice.org/50175Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>