Radio buttons with a default option do not create a variable with this option unless they are interacted with.

To reproduce:
Using the attached config.xml:
Click build with parameters
Select an option for test_var_a, do not interact with radio buttons for test_var_b
Click build

Expected result:
Build runs, with environmental variables test_var_a = <selected option> and test_var_b = opt_1

Actual result:
Build runs, with environmental variable test_var_a = <selected option> but no test_var_b environment value