Fix: Zoom-scroll extra viewports only if the mouse cursor is over the viewport. (#14209)

src/viewport_gui.cpp

@@ -124,8 +124,9 @@ public:
 		return widget == WID_EV_VIEWPORT;
 	}
 
-	void OnMouseWheel(int wheel) override
+	void OnMouseWheel(int wheel, WidgetID widget) override
 	{
+		if (widget != WID_EV_VIEWPORT) return;
 		if (_settings_client.gui.scrollwheel_scrolling != SWS_OFF) {
 			ZoomInOrOutToCursorWindow(wheel < 0, this);
 		}