Some component demos don't meet "strictNullChecks" requirements

[seanforyou23]

I noticed that when a consuming typescript app uses the strictNullChecks compiler option, errors are thrown during build time. I'm seeing this issue in the following component demos in react-integration:

• AccordionDemo/AccordionDemo.tsx
• DonutUtilizationChartDemo/DonutUtilizationGreenStaticRightDemo.tsx
• DonutUtilizationChartDemo/DonutUtilizationInvertedRightDemo.tsx
• DonutUtilizationChartDemo/DonutUtilizationSimpleBottomDemo.tsx
• DonutUtilizationChartDemo/DonutUtilizationSimpleDemo.tsx
• DonutUtilizationChartDemo/DonutUtilizationSimpleRightDemo.tsx
• DonutUtilizationChartDemo/DonutUtilizationSimpleRightGreenDemo.tsx
• DonutUtilizationChartDemo/DonutUtilizationSmallDemo.tsx
• DonutUtilizationChartDemo/DonutUtilizationSmallRightDemo.tsx
• DonutUtilizationChartDemo/DonutUtilizationSmallStaticBottomDemo.tsx
• DonutUtilizationChartDemo/DonutUtilizationSmallStaticDemo.tsx
• DonutUtilizationChartDemo/DonutUtilizationSmallStaticRightDemo.tsx
• DonutUtilizationChartDemo/DonutUtilizationStaticBottomDemo.tsx
• DonutUtilizationChartDemo/DonutUtilizationStaticDemo.tsx
• DonutUtilizationChartDemo/DonutUtilizationStaticInvertedRightDemo.tsx
• DonutUtilizationChartDemo/DonutUtilizationStaticRightDemo.tsx
• SelectDemo/SelectDemo.tsx
• TableDemo/TableActionsDemo.tsx
• TableDemo/TableSortableForCompoundExpandableDemo.tsx

It seems like a big list, but I think the problem for charts is the same one repeated in all of the chart demos. That said, I don't guess this will be a trivial fix.

Below is an example of how the error can manifest:

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[seanforyou23]

This is a critical issue, commenting so stale bot doesn't close it.

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[seanforyou23]

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