rhbz#1030009 Remove global XModel ref

...that is apparently effectively unused since
2627bdaddc6f694dc7fc6ba347a305af0f88ee2c "INTEGRATION: CWS fwk02ea: #i28639#
always used supplied status indicator" anyway but causes crashes during exit
when it holds an SwXTextDocument ref.

Change-Id: I542545c793855b41731de72650bf07d5748fcb9f