Encountered error in R code while running gene_convert_illumina.R pipeline during processing of /...

Pretty sure the line with the error message should be using result.returncode and result.stderr. Not e. Assigned myself but if anyone else wants to tackle it before I get to things today, feel free. Should be a quick fix.

https://sentry.io/greenelab/staging-refinebio/issues/667326691/

```
Encountered error in R code while running gene_convert_illumina.R pipeline during processing of /home/user/data_store/GSE98897/raw/GSM2627179-tbl-1.txt.fixed: Can't convert 'NoneType' object to str implicitly
```

Locate the error-handling code for the gene_convert_illumina.R pipeline and inspect the line that produces the shown message. Verify the available result fields and run the relevant pipeline or tests with a failing R conversion; done means the error reports the command return code and stderr instead of the missing value.

Written by the indexing model from the issue text.