Mobile concentration plot not rendering in Permeation barrier modelling

[hmonroedd]

In https://festim-workshop.readthedocs.io/en/latest/content/applications/task04.html#model-with-barrier
Error:
/tmp/ipykernel_3252/2865152383.py:23: UserWarning: No artists with labels found to put in legend. Note that artists whose label start with an underscore are ignored when legend() is called with no argument. axs[0].legend(fontsize=12, reverse=True)

It is caused by the fact that profile.times is empty so nothing is plotted
-> fix by iterating over profile.t instead. Still profile.times should be populated since timestamps are specified when doing the export

profile_exports = [
    [F.Profile1DExport](field=spe, subdomain=vol, times=[100, 17000, 8e5])
    for spe in model_barrier.species
    for vol in model_barrier.volume_subdomains
]

[RemDelaporteMathurin]

Accidentally pushed to main but it should be fix next time we buidl