The fix is twofold:
1.Get URL property from the underlying text field, not from the
text run -- put text field properties into rXPropSet (that's
what GETA macro later queries), not into rRun

6a043e9c does s/rXPropSet/rRun/
afaics for no good reason

2. Retrieve string content from URL field early, so that the test
for empty text content doesn't fire

Reviewed-on: https://gerrit.libreoffice.org/18031Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Markus Mohrhard <markus.mohrhard@googlemail.com>
Tested-by: Markus Mohrhard <markus.mohrhard@googlemail.com>

Conflicts:
	sd/qa/unit/export-tests.cxx

Change-Id: I4317e4a2f6f2e6f15c30932adc80f1227e010af0
Reviewed-on: https://gerrit.libreoffice.org/18706Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>
(cherry picked from commit e17187c3)