How do I hide 'X1 Search: Index is up-to-date' popup

I'm using X1 Client 8.3 on Windows 8.1 (x64). I often (possibly always) have a popup message in the top-left corner of the screen that says 'X1 Search: Index is up-to-date'. How do I get rid of this? I've looked for options in the X1 client and have tried clicking, right-clicking and shouting (not really). It obscures the title of the first browser tab for most browsers.

Thanks in advance.

William

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