Add Null Check when Executing Host Values

[4e6]

Pull Request Description

close #1401

Fix the execution of default arguments (represented with null values) by adding an extra null check.

Changelog:

• add: extra null check, because isNull doesn't allow null arguments

Important Notes

Checklist

Please include the following checklist in your PR:

• The documentation has been updated if necessary.
• All code conforms to the Scala, Java, and Rust style guides.
• All documentation and configuration conforms to the markdown and YAML style guides.
• All code has been tested where possible.