Fix tooltip rendering crash when activeItem is undefined (recharts#3982)

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## Description

Sometimes, the tooltip rendering would crash when the window has been
resized

> TypeError: Cannot read properties of undefined (reading 'payload')


This is due to a mistake in `getItemByXY` in
`generateCategoricalChart.tsx`.

https://github.com/recharts/recharts/blob/0d5326a8cdcad34a3b9d7c0644abbb645ddffe87/src/chart/generateCategoricalChart.tsx#L2250-L2252


https://github.com/recharts/recharts/blob/7fb227dae542c3d3093506e6d80a2c2c366f9a26/src/util/ActiveShapeUtils.tsx#L142-L152

`isFunnel`, `isPie` and `isScatter` do not check if `activeItem` is
defined, so it might cast it as a defined
`FunnelItem`/`PieItem`/`ScatterItem` even if `activeItem` is undefined

<!--- Describe your changes in detail -->

I've added a nullcheck for activeItem

## Related Issue

recharts#3981

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## Motivation and Context

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This fixes a crash

## How Has This Been Tested?

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to -->
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I manually checked that the crash doesn't happen anymore

## Screenshots (if appropriate):

<img width="1040" alt="image"
src="https://github.com/recharts/recharts/assets/8755930/9c5eaf0d-0bf4-486d-94fb-ae77b0ba8878">


## Types of changes

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- [x] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to change)

## Checklist:

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- [x] My code follows the code style of this project.
- [x] My change requires a change to the documentation.
- [x] I have updated the documentation accordingly.
- [x] I have added tests to cover my changes.
- [x] I have added a storybook story or extended an existing story to
show my changes
- [x] All new and existing tests passed.

src/util/ActiveShapeUtils.tsx

@@ -140,15 +140,15 @@ type GetActiveShapeIndexForTooltip = {
 };
 
 export function isFunnel(graphicalItem: GraphicalItem, _item: unknown): _item is FunnelItem {
-  return 'trapezoids' in graphicalItem.props;
+  return _item != null && 'trapezoids' in graphicalItem.props;
 }
 
 export function isPie(graphicalItem: GraphicalItem, _item: unknown): _item is PieItem {
-  return 'sectors' in graphicalItem.props;
+  return _item != null && 'sectors' in graphicalItem.props;
 }
 
 export function isScatter(graphicalItem: GraphicalItem, _item: unknown): _item is ScatterItem {
-  return 'points' in graphicalItem.props;
+  return _item != null && 'points' in graphicalItem.props;
 }
 
 export function compareFunnel(shapeData: FunnelItem, activeTooltipItem: FunnelItem) {