Don't export dataset file if no datasets are provided

[gerrycampion]

The downloading feature of the artifacts is functioning properly, and all the necessary files are accessible. However, I observed an issue when clicking the "Download Artifacts" button without any uploaded files or datasets. In this case, the system generates all the files and creates a zip file. Unfortunately, the Excel dataset file within the generated zip encounters an error when attempting to open it. Conversely, if datasets are uploaded and a dataset file is created, it opens without any issues. However, when the datasets section is left empty in the rule editor, the dataset file fails to open and produces an error. You can view the error in the attached screenshot. The json file for the dataset opens without any issues and is empty as it should be when no data is present.

Originally posted by @RamilCDISC in #60 (comment)

AC
If no dataset files are provided for testing, an Excel test dataset files should not be created. The other export files should be created as usual.