message: Allow tooltip's class to be reset by setting the customisation className to null.
diff: @@ -55,7 +55,7 @@ type ControlProps = Props &
  interface TooltipCustomization {
  header?: React.ReactNode;
  subheader?: React.ReactNode;
  - className?: string;
  + className?: string | null;
  }
  const TooltipContext = createContext<React.Dispatch<
  React.SetStateAction<TooltipCustomization>
  @@ -92,7 +92,7 @@ function Control({
  }: ControlProps) {
  const tooltipContents = useRef<HTMLDivElement>(null);
  const pressTipRoot = useContext(PressTipRoot);
  - const [customization, customizeTooltip] = useState<TooltipCustomization>({});
  + const [customization, customizeTooltip] = useState<TooltipCustomization>({ className: null });
  usePopper({
  contents: tooltipContents,
  @@ -167,7 +167,7 @@ export function useTooltipCustomization({
  getSubheader?: () => React.ReactNode;
  /** The CSS class(es) to be applied to the tooltip's root element. */
  - className?: string;
  + className?: string | null;
  }) {
  const customizeTooltip = useContext(TooltipContext);
  useEffect(() => {
  @@ -176,7 +176,7 @@ export function useTooltipCustomization({
  ...existing,
  ...(getHeader && { header: getHeader() }),
  ...(getSubheader && { subheader: getSubheader() }),
  - ...(className && { className }),
  + ...(className !== undefined && { className }),
  }));
  }
  }, [customizeTooltip, getHeader, getSubheader, className]);
  @@ -214,7 +214,7 @@ export const Tooltip = {
  * This does not render anything and has no effect if the calling component is not currently hosted within
  * a tooltip.
  */
  - Customize: ({ className }: { className: string }) => {
  + Customize: ({ className }: { className: string | null }) => {
  useTooltipCustomization({ className });
  return null;
  },
  