-Codechange: Simplify ScriptList iterators.

git-svn-id: svn://svn.openttd.org@26743 6aa0318a-3be1-0310-93fa-89fd2396df07
-Fix [FS6085-ish]: ScriptListSorterItemDescending::FindNext failed to detect the end.

git-svn-id: svn://svn.openttd.org@26744 6aa0318a-3be1-0310-93fa-89fd2396df07