message: Query Browser: Don't show tooltip for null values
  We use `null` values when there is a gap in the data, so no tooltip
  should be displayed for these.
diff: @@ -148,7 +148,7 @@ const TooltipInner_: React.FC<TooltipInnerProps> = ({datum, labels, query, serie
  };
  const TooltipInner = connect(tooltipStateToProps)(TooltipInner_);
  -const Tooltip: React.FC<TooltipProps> = ({datum, x, y}) => datum && _.isFinite(x) && _.isFinite(y)
  +const Tooltip: React.FC<TooltipProps> = ({datum, x, y}) => datum && _.isFinite(datum.y) && _.isFinite(x) && _.isFinite(y)
  ? <TooltipInner datum={datum} seriesIndex={datum._stack - 1} x={x} y={y} />
  : null;
  