Don't try to set special operation attributes in interface editor

[brollb]

Special operation attributes, such as displayColor, should not be attempted to be set as the default value in an operation's code when set from the interface editor.

This is related to the first stack trace in #1725. That is, the error would be avoided if this was the case. However, it is not the underlying problem for that issue so it has been moved to its own issue.