Codechange: use std::shared_ptr to manage saveload filters instead of manually trying to avoid double frees

src/openttd.cpp

@@ -966,7 +966,7 @@ static void MakeNewEditorWorld()
  * @param subdir default directory to look for filename, set to 0 if not needed
  * @param lf Load filter to use, if nullptr: use filename + subdir.
  */
-bool SafeLoad(const std::string &filename, SaveLoadOperation fop, DetailedFileType dft, GameMode newgm, Subdirectory subdir, struct LoadFilter *lf = nullptr)
+bool SafeLoad(const std::string &filename, SaveLoadOperation fop, DetailedFileType dft, GameMode newgm, Subdirectory subdir, std::shared_ptr<LoadFilter> lf = nullptr)
 {
 	assert(fop == SLO_LOAD);
 	assert(dft == DFT_GAME_FILE || (lf == nullptr && dft == DFT_OLD_GAME_FILE));