Fixed a bug that the next commit's test helped me find. In CopyWithModification, we also have to recalculate Invalid if any of the excludes change (and were calculating that wrong anyway)
Fixed a bug that the next commit's test helped me find. In CopyWithModification, we also have to recalculate Invalid if any of the excludes change (and were calculating that wrong anyway)

jkomoros/sudoku,jkomoros/sudoku,jkomoros/sudoku