Only call getScDocument when needed

Change-Id: I2dca76af46e63b5dd833f5a60549d4b1a7b03d84
Reviewed-on: https://gerrit.libreoffice.org/1861Reviewed-by: Olivier Hallot <olivier.hallot@alta.org.br>
Tested-by: Olivier Hallot <olivier.hallot@alta.org.br>

sc/source/filter/oox/stylesbuffer.cxx

@@ -2715,11 +2715,11 @@ void CellStyle::createCellStyle()
     if( !mbCreated )
         mbCreated = maFinalName.isEmpty();
 
-    ::ScDocument& rDoc = getScDocument();
     if( !mbCreated && !mpStyleSheet )
     {
         bool bCreatePattern = false;
         Xf* pXF = getStyles().getStyleXf( maModel.mnXfId ).get();
+        ::ScDocument& rDoc = getScDocument();
 
         bool bDefStyle = maModel.isDefaultStyle();
         if( bDefStyle )