tdf#121172: use first polygon

This was a code reading mistake of me when preparing commit
3040d328c944d91b0cd612d86d358823b5c5b883.

Change-Id: I321f1f39e5600fcd786ba6d2e7a4b9444021bcff
Reviewed-on: https://gerrit.libreoffice.org/62886
Tested-by: Jenkins
Reviewed-by: Mike Kaganski <mike.kaganski@collabora.com>
diff --git a/xmloff/source/draw/shapeexport.cxx b/xmloff/source/draw/shapeexport.cxx
index 3dbb2b5..d022ba3 100644
--- a/xmloff/source/draw/shapeexport.cxx
+++ b/xmloff/source/draw/shapeexport.cxx
@@ -2055,9 +2055,9 @@ void XMLShapeExport::ImpExportLineShape(
    if (auto pSourcePolyPolygon
            = o3tl::tryAccess<drawing::PointSequenceSequence>(aAny))
    {
        if (pSourcePolyPolygon->getLength() > 1)
        if (pSourcePolyPolygon->getLength() > 0)
        {
            const drawing::PointSequence& rInnerSequence = (*pSourcePolyPolygon)[1];
            const drawing::PointSequence& rInnerSequence = (*pSourcePolyPolygon)[0];
            if (rInnerSequence.getLength() > 0)
            {
                const awt::Point& rPoint = rInnerSequence[0];