Don't crash when opening templates via WebDAV

When loading a ODT template via HTTP, it crashes LO with an
lang::IllegalArgumentException in LockFileCommon::ResolveLinks.
This happens when closing the loaded template, as LO tries to
remove a not-existing lock. aDocURL at this point is empty, so
HasError() is true.

As stated in the comment, we don't need a lock for documents
created from templates, as this opens an internal copy of the
document, so don't mark the teplate document as locked.

Change-Id: Ide60020b6287aa67861dbcc8ec1b94f37896b7ef
Reviewed-on: https://gerrit.libreoffice.org/42485
Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Jan-Marek Glogowski <glogow@fbihome.de>
diff --git a/sfx2/source/doc/docfile.cxx b/sfx2/source/doc/docfile.cxx
index f37a6c6..7437c66 100644
--- a/sfx2/source/doc/docfile.cxx
+++ b/sfx2/source/doc/docfile.cxx
@@ -1005,15 +1005,16 @@ void SfxMedium::LockOrigFileOnDemand( bool bLoading, bool bNoUI )
        try
        {
            bool bResult = pImpl->m_bLocked;
            bool bIsTemplate = false;
            // so, this is webdav stuff...
            if ( !bResult )
            {
                // no read-write access is necessary on loading if the document is explicitly opened as copy
                const SfxBoolItem* pTemplateItem = SfxItemSet::GetItem<SfxBoolItem>(GetItemSet(), SID_TEMPLATE, false);
                bResult = ( bLoading && pTemplateItem && pTemplateItem->GetValue() );
                bIsTemplate = ( bLoading && pTemplateItem && pTemplateItem->GetValue() );
            }

            if ( !bResult && !IsReadOnly() )
            if ( !bIsTemplate && !bResult && !IsReadOnly() )
            {
                ShowLockResult bUIStatus = ShowLockResult::NoLock;
                do