fix: handle NA values correctly in meta compare pathways (#134)

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## Summary by CodeRabbit

- **Bug Fixes**
	- Improved handling of missing values when reading CSV files.

- **Documentation**
	- Clarified the interpretation of null values in data processing.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Co-authored-by: Addimator <adpri100@hhu.de>

workflow/scripts/compare_pathways.py

@@ -5,8 +5,8 @@
 
 sys.stderr = open(snakemake.log[0], "w")
 
-diffexp_x = pl.read_csv(snakemake.input[0], separator="\t").lazy()
-diffexp_y = pl.read_csv(snakemake.input[1], separator="\t").lazy()
+diffexp_x = pl.read_csv(snakemake.input[0], separator="\t", null_values="NA").lazy()
+diffexp_y = pl.read_csv(snakemake.input[1], separator="\t", null_values="NA").lazy()
 label_x = list(snakemake.params.labels)[0]
 label_y = list(snakemake.params.labels)[1]