Dynamically changing decal with "Set decalmaterial" not working

I have a widget with an editable text and a button:


Inside the eventgraph of that widget i have this:

This is how my asset (tester) looks like wit the decal:

When i fill in nothing and click my button, the decal inside **tester **will be green.
When i fill in image.jpg the decal inside **tester **also becomes green,

before button click: https://snipboard.io/CtTHwr.jpg
after button click: https://snipboard.io/1vBA7Q.jpg