Basically we could end up in a situation where the plotInfo is no longer
valid, yet the model changes and triggers a redraw before the new data is
passed into the TankBar.
Instead of chasing that race condition it seemed much easier to just copy
the plot_data entries and the gas information in the dive.
Fixes#716
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>