Max Partition Availability Lag (ms) in the get consuming segments panel has an odd fallback mechanism

**Current usage:** its used to measure the lag in ms between the last offset consumed and the last offset produced
**Issue:** in case the kafka topic is not reachable or is timing out, the offset just shows the epoch in ms, which is confusing, we should aim to have a definite error code or something of the sort, which would make it clear.