Turn off tooltips if no dives are selected

We already clear the widgets but forgot to turn off the tooltips as well.

Reported-by: Sergey Starosek <sergey.starosek@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Clear the list of events when closing data file

When the data file is closed we should reset the events that we offer for
filtering.

Reported-by: Sergey Starosek <sergey.starosek@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>