Prevent reconnection in same tab causing duplication

[celynw]

When reconnecting to an existing tab, it reinitialises, which duplicates the columns.

I've seen this happen when I have two tabs open and connected at the same time. When closing one of them, the server thinks it has lost connection, so tries to reconnect. This succeeds to the already open second tab.

I think this could happen in normal conditions if the network is interrupted somehow, so I'd like to gracefully handle this.