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/42485Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Jan-Marek Glogowski <glogow@fbihome.de>

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