I have registered external function:

 

trimWhitespace (text)

 

  if (text == null) return text;

  return text = text.trim();

 

 

If I put this function in indexed calculation field, question mark is displayed instead of text. Is it a bug?

how about 

if(text != null){
return text.trim()
}

but is there any reason to not use the TrimAll function that is already in FileMaker???