Custom Function in FlutterFlow Returns Empty List When Filtering Unique Strings

Hello, community! I'm facing an issue with a custom function in FlutterFlow. My goal is to create a function that takes a list of JSON elements, filters out empty strings, and returns a list of unique, non-empty strings
Here is the code I'm using for this function:

List<String>? filterUniqueStrings(List<dynamic>? elements) {

  if (elements == null || elements.isEmpty) {
    print("Input list is null or empty");
    return [];
  }

  print("Received elements: $elements");

  Set<String> uniqueStrings = {};

  for (var element in elements) {
    print("Processing element: $element");

    if (element is String) {
      print("Element is a string: $element");

      if (element.isNotEmpty) {
        print("Adding non-empty string: $element");
        uniqueStrings.add(element);
      } else {
        print("Skipping empty string");
      }
    } else {
      print("Skipping non-string element: $element");
    }
  }

  print("Unique strings: $uniqueStrings");

  return uniqueStrings.toList();

}

I tested this function with the following input: ["Hello", "", "World", "Hello", "Test", ""]

Expected output: ["Hello", "World", "Test"]
Actual output: [] (empty list)

The function is configured in FlutterFlow with these settings:

Input: JSON (List<JSON>, Nullable)
Output: List<String>, Nullable

What could be the reason for this behavior? Am I missing something in the way the function is configured or implemented? Any guidance would be greatly appreciated!"