Items from `index.tag` are stored as plain JS objects when no metatable
is defined. The `group by` clause wraps rows in `LuaTable` (`key`,
`group`) but leaves the individual `group` items as plain JS objects.
This causes `t.keys is not a function` errors when passing `row.group`
to APIs like `template.each` that expect `LuaTable` instances.
Signed-off-by: Matouš Jan Fialka <mjf@mjf.cz>
Matouš Jan Fialka
879bfb811a