tdf#126588 crash in saving view

tdf#126588 crash in saving view

regression from
    commit d425658bd9fd8e315e4931afb544bc845da0360e
    Date:   Wed Dec 19 16:10:51 2018 +0200
    pass OSQLParseNode around by unique_ptr

We have a OSQLNode being deleted at
connectivity::OSQLParseNodesContainer::clearAndDelete() at
connectivity/source/parse/sqlnode.cxx:2781
connectivity::OSQLParser::parseTree(rtl::OUString&, rtl::OUString
const&, bool)
(this=0x38eba90, rErrorMessage="syntax error, unexpected UNION,
expecting $end", rStatement="CREATE VIEW \"View1\" AS SELECT
\"Tab1\".\"Name\" AS \"Name1\", \"Tab1\".\"Geburtsdatum\" AS
\"Geburtsdatum1\", 1 AS \"MonatZahl1\",
COALESCE(\"Tab1\".\"MonatZaehler\",999) AS \"MonatZaehler1\", 'Januar'
AS \"Monat1\", \"Tab2"..., bInternational=false)
    at workdir/YaccTarget/connectivity/source/parse/sqlbison.cxx:10914
namespace)::parseStatement_throwError(connectivity::OSQLParser&,
rtl::OUString const&,
com::sun::star::uno::Reference<com::sun::star::uno::XInterface> const&)
(_rParser=..., _rStatement="CREATE VIEW \"View1\" AS SELECT
\"Tab1\".\"Name\" AS \"Name1\", \"Tab1\".\"Geburtsdatum\" AS
\"Geburtsdatum1\", 1 AS \"MonatZahl1\",
COALESCE(\"Tab1\".\"MonatZaehler\",999) AS \"MonatZaehler1\", 'Januar'
AS \"Monat1\", \"Tab2"..., _rxContext=uno::Reference to
(dbaccess::OSingleSelectQueryComposer *) 0x38eb8d0)
    at dbaccess/source/core/api/SingleSelectQueryComposer.cxx:106

and then again at
std::unique_ptr<connectivity::OSQLParseNode,
std::default_delete<connectivity::OSQLParseNode>
>::operator=(decltype(nullptr))
(this=0x38eba90) at connectivity/source/parse/sqlnode.cxx:1500

Change-Id: I292627a06369208e0010743063c7eb5a38921a19
Reviewed-on: https://gerrit.libreoffice.org/77106
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>