UI doesn't show node info for mixed clusters (when 7.0 node added but not rebalanced in yet)

I see that when 7.1 node joins 6.5 cluster, 7.0 node can't show node information in the UI (I see spinners when clicking any node). Note that it happens after node addition but before rebalance.
I seems to me that it happens because /_uistats returns "Uknown hostname" error for nodes that are added but not yet rebalanced in. I see that in 6.5 /_uistats returned the same error and the UI could handle that error, but in 7.1 it seems that it doesn't, so it is a regression.

I saw it in 7.1, but I haven't tested it in 7.0. Most likely 7.0 is affected as well.