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

src/string_base.h

@@ -28,7 +28,7 @@ public:
 	 */
 	static std::unique_ptr<StringIterator> Create();
 
-	virtual ~StringIterator() {}
+	virtual ~StringIterator() = default;
 
 	/**
 	 * Set a new iteration string. Must also be called if the string contents