[VOTE] KIP-1140: Avoid to return null value in Map from public api of consumer

[黃竣陽]

Hello all

I would like to call a vote on KIP-1140: Avoid to return null value in Map from 
public api of consumer

KIP:
<https://cwiki.apache.org/confluence/x/mIuMEw>

Discussion thread:
<https://lists.apache.org/thread/yj965clqfq3dxo99vzjhmw2vltc1j0dd>

Best Regards,
Jiunn-Yang