fix crash in CertificateChooser for GPG

mvUserData is still needed to keep it's content from being deleted.

Revert "Drop unused instance variable."

This reverts commit 687ae6ca01.

Change-Id: I689cfdaf8d4d62a3b53ff7fb318dc8c70b9e1c2d
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/167020
Reviewed-by: Thorsten Behrens <thorsten.behrens@allotropia.de>
Tested-by: Jenkins

compilerplugins/clang/unusedfields.writeonly.results

@@ -1351,6 +1351,8 @@ xmloff/source/forms/officeforms.hxx:68
 xmloff/source/text/txtimp.cxx:104
     XMLTextImportHelper::Impl m_xFrameImpPrMap rtl::Reference<SvXMLImportPropertyMapper>
 xmlsecurity/inc/certificatechooser.hxx:57
+    CertificateChooser mvUserData std::vector<std::shared_ptr<UserData> >
+xmlsecurity/inc/certificateviewer.hxx:51
     CertificateViewer mxGeneralPage std::unique_ptr<CertificateViewerGeneralTP>
 xmlsecurity/inc/certificateviewer.hxx:52
     CertificateViewer mxDetailsPage std::unique_ptr<CertificateViewerDetailsTP>

xmlsecurity/inc/certificatechooser.hxx

@@ -51,6 +51,7 @@ class CertificateChooser final : public weld::GenericDialogController
 {
 private:
     std::vector< css::uno::Reference< css::xml::crypto::XXMLSecurityContext > > mxSecurityContexts;
+    std::vector<std::shared_ptr<CertificateChooserUserData>> mvUserData;
 
     bool                    mbInitialized;
     CertificateChooserUserAction const meAction;

xmlsecurity/source/dialogs/certificatechooser.cxx

@@ -217,6 +217,9 @@ void CertificateChooser::ImplInitialize(bool mbSearch)
             userData->xSecurityContext = secContext;
             userData->xSecurityEnvironment = secEnvironment;
 
+            // Needed to keep userData alive. (reference to shared_ptr prevents delete)
+            mvUserData.push_back(userData);
+
             OUString sIssuer = xmlsec::GetContentPart( xCert->getIssuerName(), xCert->getCertificateKind());
             OUString sExpDate = utl::GetDateString(xCert->getNotValidAfter());