Generate Release Notes needs to require the Environment Variable field to be set or provide a default as when that field is empty, Windows jobs fail with java.io.IOException: CreateProcess error=87, The parameter is incorrect.

Steps to Reproduce:

1. Create a Freestyle Job
2. Enable Generate Release Notes and do not fill in the Environment Variable field
3. Add a build step to Execute Windows batch command put set in the command
   • The single set command should print the environment on a successful run
4. Run the build and it should error out when trying to execute cmd with java.io.IOException: CreateProcess error=87, The parameter is incorrect.