fix unhandled exception terminate on ooo48061-1.sxw

Change-Id: Ibacb94e719f42faa87ece48051ed8f72c3c78d02
DBG_ASSERT->assert when followed by dereference

Change-Id: I9390228721df1b713d8cf2e719854b74d6b639c8
fix assert for empty string case on loading ooo119654-1.odt

Change-Id: I97cbb6ff0f320d9315310cbc06c52c3c4f958a64