Pass Parameter to Sub UDT

I have a UDT (B) with a UDT (A) inside. I'm passing a (string) parameter to the sub-UDT via {parameter} in the parameter setup page within the UDT definition.

The parameter is used for extra information on an alarm's display path, if needed. Parameters are configured like so:

{Display_Path_b} | UDT_B
{Display_Path_a} | UDT_A

Within the definition for UDT_B, the Display_Path_a parameter is filled in with {Display_Path_b} so that the parameter can be passed down.

However, when there is no extra information to display in the display path, it's left blank. In that case, the literal string '{Display_Path_b}' is used.

Why is an empty string not passed to the sub UDT?

As a workaround, my UDT definition now contains a space for that display path property.