Make use of the new resource manager's purgeable flag

src/scenedit/scen.main.cpp

@@ -118,7 +118,7 @@ void init_scened(int argc, char* argv[]) {
 	mainPtr.create(sf::VideoMode(windRect.width(), windRect.height()), "Blades of Exile Scenario Editor", sf::Style::Titlebar | sf::Style::Close);
 	mainPtr.setPosition(windRect.topLeft());
 #ifndef __APPLE__ // This overrides Dock icon on OSX, which isn't what we want at all
-	const ImageRsrc& icon = ResMgr::graphics.get("icon");
+	const ImageRsrc& icon = ResMgr::graphics.get("icon", true);
 	mainPtr.setIcon(icon->getSize().x, icon->getSize().y, icon->copyToImage().getPixelsPtr());
 #endif
 	init_menubar(); // This is called twice because Windows and Mac have different ordering requirements