unnecessary null pointer check before delete

Change-Id: I16d48a501353b45e2d6c8cc0de49f3da0709eabe
support export of property mapping

Change-Id: I9529eedb9c9c002bfc2fee638938082cef59f185
fix OOXML strict chart import

Change-Id: I84a2fd575ced64d4774147063f13ebb8605c100f