Handle bad SwWW8ImplReader::GetCol input

With previously found offenders out of the way, looks like
sw/qa/core/data/ww8/pass/CVE-2009-3302-2.doc is the only case that triggers
this, and that is likely deliberately malformed input.

As the whole ww8 parser appears not to be build around robust eager input
validation and error signalling, there is little more we can do here than throw
up our hands in despair.

Change-Id: Idf61fcf14a784cef1539654f2825c013c218987f