How to "do nothing" as an option in an if /else statement

[mike cohen 3]

Product: Tibco cloud integration.

I am new to tibco cloud integration and am trying to convert our old scribe insight maps. In scribe insight map the term #NULL! would tell scribe to "do nothing" to the target record.

I could use this like If (Source value = NULL thentargetvalue = 1, #NULL!)

I am trying to replicate this in TCI and can't get the #NULL! portion to work, TCI keeps overwriting my target data with NULL when I want TCI to do nothing.

How can I implement.

 

IF = NULL then = 1

Else (do nothing to target)

 

I've tried

IF(ISNULLORWHITESPACE(sourcevalue), target=1, NULL) - overwrites target with null

IF(ISNULLORWHITESPACE(sourcevalue), target=1, "") - overwrites target with blank

 

IF(ISNULLORWHITESPACE(sourcevalue)) ---- wont validate