Resolves: tdf#121887 RowModel::mnRow is 1-based, always

Basically this was always wrong.

Original code didn't treat the r attribute as optional and
resulted in an invalid -1 row for such cases, hence the RowModel
wasn't applied later.

Then

commit af8e6f4f
CommitDate: Wed May 29 22:05:02 2013 +0200

    r is an optional attribute in c and r, fdo#65059

introduced a 0-based SheetDataContext::mnRow but assigned that to
a 1-based RowModel::mnRow as well if r attribute was missing, and
did not update SheetDataContext::mnRow if r attribute was given.

commit ff56553e
CommitDate: Thu Mar 13 18:39:22 2014 -0400

    fdo#76032: This row index is 1-based whereas our own mnRow is 0-based.

then correctly assigned the decremented r attribute to
SheetDataContext::mnRow but did not touch the assignment to
RowModel::mnRow if r was not given. Probably confused by the
++mnRow already there which is correct but not sufficient for the
assignment.

Which we now finally fix herewith..

Change-Id: Iae1563ed01b95e7852ddad4fd59374c07186b493
Reviewed-on: https://gerrit.libreoffice.org/64580
Tested-by: Jenkins
Reviewed-by: Eike Rathke <erack@redhat.com>

sc/source/filter/oox/sheetdatacontext.cxx

@@ -275,7 +275,7 @@ void SheetDataContext::importRow( const AttributeList& rAttribs )
         mnRow = nRow-1; // to 0-based row index.
     }
     else
-        aModel.mnRow = ++mnRow;
+        aModel.mnRow = (++mnRow + 1);   // increment 0-based row index, to 1-based model row
     mrAddressConv.checkRow( mnRow, true);
     mnCol = -1;