In my testing on Windows, the crashing scenario was this:
1. FileDialogHelper_Impl::updateVersions() creates storage calling
   comphelper::OStorageHelper::GetStorageFromURL;
2. Content::openStream() calls isDocument first;
3. Content::isDocument() indirectly initiates WebDAV session,
   creating a NeonSession;
4. All operations of NeonSession call Init() first; its first call
   initializes m_pHttpSession using ne_session_create, and then
   adds auth callbacks using ne_add_server_auth/ne_add_proxy_auth
5. Then NeonSession performs the rest of PROPFIND task, calling
   ah_post_send and auth_challenge; the latter fails, then
   ah_post_send calls clean_session, which cleans m_pHttpSession's
   auth_session's sspi_host;
6. NeonSession::HandleError throws DAVException for NE_AUTH error;
7. Content::isDocument() returns true to Content::openStream(),
   which proceeds to execute the command, which in turn re-uses
   the NeonSession and its m_pHttpSession;
8. NeonSession::OPTIONS then indirectly calls continue_sspi, which
   tries to dereference the m_pHttpSession's auth_session's
   sspi_host which is nullptr at this point.

So in case NeonSession detects the NE_AUTH error condition, let's
set a flag indicating that the next Init() should reinitialize its
m_pHttpSession.

Also fixed a case when xProps was used before initialization in
Content::getPropertyValues.

Change-Id: Ifc9eec4fe0333ff6be17c5089068441b4a6eb78c
Reviewed-on: https://gerrit.libreoffice.org/65950
Tested-by: Jenkins
Reviewed-by: Mike Kaganski <mike.kaganski@collabora.com>