bug: introduction of meta attribute broke heatmaps

[pfebrer]

This fixes a bug introduced in #621. I also added some extra tests.

[codecov]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (31f5dfd) 87.26% compared to head (4f40f21) 87.70%.
Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #623      +/-   ##
==========================================
+ Coverage   87.26%   87.70%   +0.44%     
==========================================
  Files         357      360       +3     
  Lines       47732    47792      +60     
==========================================
+ Hits        41652    41918     +266     
+ Misses       6080     5874     -206     

Files	Coverage Δ
src/sisl/viz/figure/figure.py	45.00% <100.00%> (+2.27%)	⬆️
src/sisl/viz/figure/matplotlib.py	37.15% <100.00%> (+19.67%)	⬆️
src/sisl/viz/plots/tests/test_bands.py	100.00% <100.00%> (ø)
src/sisl/viz/plots/tests/test_geometry.py	100.00% <100.00%> (ø)
src/sisl/viz/plots/tests/test_grid.py	100.00% <100.00%> (ø)
src/sisl/viz/plots/tests/test_pdos.py	100.00% <100.00%> (ø)
src/sisl/viz/figure/plotly.py	38.36% <66.66%> (+12.85%)	⬆️

... and 11 files with indirect coverage changes

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.