Bugfix: macrosynergy.visuals, safely failing when "seaborn-darkgrid" style is not available

[Magnus167]

No description provided.

[codecov]

Codecov Report

Merging #1075 (9e320a2) into develop (4eb0baf) will increase coverage by 0.02%.
Report is 1 commits behind head on develop.
The diff coverage is 37.50%.

❗ Current head 9e320a2 differs from pull request most recent head 0de6024. Consider uploading reports for the commit 0de6024 to get more accurate results

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1075      +/-   ##
===========================================
+ Coverage    65.21%   65.24%   +0.02%     
===========================================
  Files           45       45              
  Lines         5086     5093       +7     
===========================================
+ Hits          3317     3323       +6     
- Misses        1769     1770       +1     

Files	Coverage Δ
macrosynergy/visuals/plotter.py	72.52% <37.50%> (-3.67%)	⬇️

... and 1 file with indirect coverage changes