sp: skip allocation of aggr_node->ts if cmd->timeseries_num == 0
sp: skip allocation of aggr_node->ts if cmd->timeseries_num == 0

This PR skips skip allocation of aggr_node->ts if cmd->timeseries_num == 0

Signed-off-by: Yong Tang <765086fe2e0c1f980161f127fec596800f327f62@outlook.com>

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