Try adding a BindingResult parameter to methods annotated with @RequestMapping which have a @ModelAttribute annotated parameters. After each @ModelAttribute parameter, Spring looks for a BindingResult in the next parameter position (order is important).
So try changing:
@RequestMapping(method = RequestMethod.POST)
public String loadCharts(HttpServletRequest request, ModelMap model, @ModelAttribute("sideForm") Chart chart)
...
To:
@RequestMapping(method = RequestMethod.POST)
public String loadCharts(@ModelAttribute("sideForm") Chart chart, BindingResult bindingResult, HttpServletRequest request, ModelMap model)
...