Getting "Missing Parameter" Response even though WSDL describes it as optional field

Thank you for response! I believe I finally got past it by finding this forum post:

https://community.smartbear.com/t5/SoapUI-Open-Source/REST-request-does-not-contain-parameter-if-value-is-an-empty/td-p/9146

I had to make the parameter required even though it's value is blank.

Now the next issue I am running into is that one of my parameters is a Base64Binary type and keeping that value as blank triggers an error saying: "Cannot convert to System.Byte.  Input string was not in a correct format" error.