Expected a value variable in cond but missing: Accepting empty variables

This error has been addressed here, here and partially here.

It happens if one of the 3 cond fields uses an empty variable.

The problem is we cannot always be sure the variables will be assigned nodes.

If the variable is the condition and is empty, the condition could be always interpreted as false.

Even though I usually I don’t even care about the result if the variable is empty.

Is there any way to handle such cases?