tdf#118374: fix crash from loplugin:useuniqueptr in sdext

See bt:
https://bugs.documentfoundation.org/attachment.cgi?id=143105

Regression from:
https://cgit.freedesktop.org/libreoffice/core/commit/?id=a9ef943769b06e6bdffe7326f288b27e08a95698

Change-Id: I285f00cb6ede3d952a794b60ff64586fe2224e5f
Reviewed-on: https://gerrit.libreoffice.org/56490Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>
Tested-by: Jenkins
Reviewed-by: Julien Nabet <serval2412@yahoo.fr>

sdext/source/pdfimport/tree/genericelements.cxx

@@ -447,7 +447,6 @@ void PageElement::resolveUnderlines( PDFIProcessor const & rProc )
             auto next_it = poly_it;
             ++next_it;
             Children.erase( poly_it );
-            delete pPoly;
             poly_it = next_it;
         }
         else

sdext/source/pdfimport/tree/writertreevisiting.cxx

@@ -419,7 +419,6 @@ void WriterXmlOptimizer::visit( PolyPolyElement& elem, const std::list< std::uni
 #else
         elem.Parent->Children.erase(next_it);
 #endif
-        delete pNext;
     }
 }
 
@@ -819,7 +818,6 @@ void WriterXmlOptimizer::optimizeTextElements(Element& rParent)
                     pCur->Children.splice( pCur->Children.end(), pNext->Children );
                     // get rid of the now useless element
                     rParent.Children.erase( next );
-                    delete pNext;
                     bConcat = true;
                 }
             }