SmXMLExport::GetViewSettings: add back lost property name

This was removed in 90a91ed3e9ca1684655268dc52754ca569febc36, probably
accidently.

Change-Id: Ib5b4bc847caaa1fb2f119b07612231e32789834e
diff --git a/starmath/source/mathmlexport.cxx b/starmath/source/mathmlexport.cxx
index d87195d..654809d 100644
--- a/starmath/source/mathmlexport.cxx
+++ b/starmath/source/mathmlexport.cxx
@@ -673,6 +673,7 @@ void SmXMLExport::GetViewSettings( Sequence < PropertyValue >& aProps)
    pValue[nIndex].Name = "ViewAreaLeft";
    pValue[nIndex++].Value <<= aRect.Left();

    pValue[nIndex].Name = "ViewAreaWidth";
    pValue[nIndex++].Value <<= aRect.GetWidth();

    pValue[nIndex].Name = "ViewAreaHeight";