The m_xStartingRange is null at this point for whatever reason,
and the block immediately above this one already checks
xRangeProperties, so let's just do the same here. (Also IsNewDoc(),
where the logic between PageDescName and PageNumberOffset presumably
shouldn't differ?).

(started to crash with abaf6bde
 as previously that code was unreachable in RTF import)

Change-Id: I20539c3a753ecea357e556ea556c3c26983ce1d1