Fix double free bug when server is shut down

Zeno- · Zeno- · commit f0a8f655c0d5 · 2014-11-15T22:33:52.000+10:00
Thanks @oleastre
diff --git a/src/mapgen.h b/src/mapgen.h
@@ -136,6 +136,7 @@ struct MapgenFactory {
 
 class GenElement {
 public:
+	virtual ~GenElement() {}
 	u32 id;
 	std::string name;
 };
