Yes, you need to vote. In the quorum section of the DEF 14A:
Broker non-votes and abstentions will be counted for purposes of determining the presence of a quorum, but will not be voted FOR or AGAINST a proposal. Accordingly, abstentions and broker non-votes effectively will be a vote against any proposal where the required vote is a percentage of the shares present or outstanding. Broker non-votes and abstentions will not be counted as votes cast for purposes of determining whether sufficient votes have been received to approve a proposal. However, abstentions and non-votes will operate as a vote against the proposal to authorize the Board to withdraw the Company’s election to be regulated as a BDC.