Worked on the geotools/geotools repository to enhance backend stability by addressing a NullPointerException in the transformer sorting flow. Focused on improving the robustness of the Transformer.getTransformedSortBy method by introducing a null check to prevent errors when closing the feature iterator. Developed and integrated a regression test to ensure that NATURAL_ORDER sorting no longer triggers an exception, thereby increasing reliability for clients relying on sort-based transformations. Utilized Java for both the bug fix and testing, emphasizing careful regression coverage and maintenance of existing behavior. The work contributed to improved client stability and more dependable backend data processing.