[fix] fix ValueError when plotting events components

[johnnykwan21]

🔬 Background

Fixed ValueError when plotting events components using plot_parameters method inside forecaster.py, see #1366

🔮 Key changes

Simple fixing check_if_configured & get_valid_configuration function inside plot_utils.py

📋 Review Checklist

• I have performed a self-review of my own code.
• I have commented my code, added docstrings and data types to function definitions.
• I have added pytests to check whether my feature / fix works.

Please make sure to follow our best practices in the Contributing guidelines.

[codecov]

Codecov Report

Merging #1368 (b1dddb1) into main (50d5e41) will increase coverage by 0.00%.
The diff coverage is 81.48%.

@@           Coverage Diff           @@
##             main    #1368   +/-   ##
=======================================
  Coverage   89.85%   89.85%           
=======================================
  Files          38       38           
  Lines        5084     5086    +2     
=======================================
+ Hits         4568     4570    +2     
  Misses        516      516           

Files	Coverage Δ
neuralprophet/plot_utils.py	88.05% <81.48%> (+0.08%)	⬆️

[leoniewgnr]

Hi, looks really good! Thanks for fixing it! Would you mind adding a test to it, so that the code coverage is fulfilled and we won't run into that problem again?

[SimonWittner]

Closed with #1434