Codechange: use default dtor instead of empty (#10826)

src/linkgraph/demands.h

@@ -37,7 +37,7 @@ public:
 	/**
 	 * Virtual destructor has to be defined because of virtual Run().
 	 */
-	virtual ~DemandHandler() {}
+	virtual ~DemandHandler() = default;
 };
 
 #endif /* DEMANDS_H */