Liquid Exception: undefined method `[]' for nil:NilClass

[icarosadero]

I installed the version 0.2.0 of jekyll-figure and got this error while trying to serve the site locally:

 Liquid Exception: undefined method `[]' for nil:NilClass in /home/<USER>/Documents/notes/_posts/2024-03-02-ecg.md
/mnt/secondary/cache/bundle/ruby/3.0.0/gems/jekyll-figure-0.2.0/lib/utils.rb:42:in `print_reference': undefined method `[]' for nil:NilClass (NoMethodError)

I have these plugins in my config.yml:

plugins:
  - jekyll-mermaid
  - jekyll-feed
  - jekyll/scholar
  - jekyll-figure

On the blog post that it references, I am trying to add figures like this:

{% figure caption:"Theoretical Schematic of an ECG circuit." label:"fig_schematic "%}
![Theoretical Schematic of the ECG circuit.]({{ site.baseurl }}/assets/images/2024/2024-03-02-ecg/ecg/ecg_simple.svg){: width="80%" }
{% endfigure %}

And call them with figref: {% figref fig_schematic %}

Any ideas how to fix this?