Prevent empty convergence plot Error when n_iteration=1

[DeerWhale]

📝 Description

Type: 🪲 bugfix

When running a tardis simulation with n_iteration =1 in the config file and export_convergence_plots=True, the simulation can be successfully returned due to an error that caused by a empty plot in the convergence_plots.

Hence, adding an argument to check if the plots inside simulation.convergence_plots is empty before export the convergence_plot.

🚦 Testing

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☑️ Checklist

• I requested two reviewers for this pull request
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• I built the documentation by applying the build_docs label

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[codecov]

Codecov Report

Merging #2371 (5e2c690) into master (9107f26) will decrease coverage by 1.61%.
Report is 12 commits behind head on master.
The diff coverage is 31.55%.

❗ Current head 5e2c690 differs from pull request most recent head 83894c2. Consider uploading reports for the commit 83894c2 to get more accurate results

@@            Coverage Diff             @@
##           master    #2371      +/-   ##
==========================================
- Coverage   72.14%   70.53%   -1.61%     
==========================================
  Files         137      138       +1     
  Lines       12507    12866     +359     
==========================================
+ Hits         9023     9075      +52     
- Misses       3484     3791     +307     

Files Changed	Coverage Δ
.../montecarlo/montecarlo_numba/single_packet_loop.py	24.28% <0.00%> (ø)
tardis/montecarlo/montecarlo_numba/vpacket.py	20.35% <0.00%> (ø)
tardis/transport/r_packet_transport.py	17.77% <0.00%> (ø)
tardis/visualization/widgets/grotrian.py	0.00% <0.00%> (ø)
tardis/analysis.py	31.83% <14.63%> (-2.02%)	⬇️
tardis/montecarlo/montecarlo_numba/macro_atom.py	53.12% <16.66%> (ø)
tardis/montecarlo/montecarlo_numba/r_packet.py	60.60% <25.00%> (ø)
tardis/montecarlo/montecarlo_numba/interaction.py	28.16% <26.92%> (ø)
tardis/montecarlo/montecarlo_numba/opacities.py	38.18% <33.33%> (ø)
tardis/util/base.py	73.07% <37.50%> (-1.13%)	⬇️
... and 18 more

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[sonachitchyan]

Do we know/care why docstr-cov fails here? @andrewfullard

[sonachitchyan]

Do we know/care why docstr-cov fails here? @andrewfullard

okay the fail seems irrelevant to the PR here?