Formatted string function not executed when input variable is empty

[JohannaOtt]

Version 4.0.0.SNAPSHOT Build 617913794

When defining a Formatted string function with several input variables and e.g. aligning the values in the function, it does not get executed (target attribute is empty) as soon as one of the input variables is empty. While this might be desired for Formatted string functions with one single input variable (but even in this case, it could be discussed to still write the information added in the function to the target attribute), it should not affect the execution of the function for cases with several input variables. If users should be aware that the output might not be complete/as expected because one of the input variables is empty, this could be added as warning for the transformation.