backends/chert/chert_btreebase.cc,backends/chert/chert_table.cc: The
table is sync-ed after the base file, so it's the last table we want
to full-sync, not the last base file.

git-svn-id: file:///home/xapian-svn/xapian/trunk@18275 6b2f1b92-a4f3-0310-943f-de3cbe41748b