Fix an assertion to avoid crash on deletions in Recent root.

                String id, DocumentStack stack, List<DocumentInfo> srcs,

                DocumentInfo srcParent) {

            assert(!srcs.isEmpty());

            assert(stack.peek().isDirectory());  // we can't currently delete from archives.

            // stack is empty if we delete docs from recent.

            // we can't currently delete from archives.

            assert(stack.isEmpty() || stack.peek().isDirectory());

            return new DeleteJob(service, appContext, listener, id, stack, srcs, srcParent);

        }

    }