Fix scrollbar errors when offset is zero

[pradeepnschrodinger]

Description

This fixes the issue seen at #723.
The onmousedown handler for Scrollbar throws an error when the user tries to scroll at the beginning of the scroll content area, which happens because targetTouches is undefined at:

fixed-data-table-2/src/plugins/Scrollbar.js

Lines 527 to 537 in 522e82b

	getTouchX = (/*object*/ e) => {
	return Math.round(
	e.targetTouches[0].clientX - e.target.getBoundingClientRect().x
	);
	};
	getTouchY = (/*object*/ e) => {
	return Math.round(
	e.targetTouches[0].clientY - e.target.getBoundingClientRect().y
	);
	};

because we're actually doing a normal mouse click instead of a "touch" click.
But the code shouldn't have reached here in the first place.

The root problem is that FDT thinks it's a touch event because of the way we use the || operator in

fixed-data-table-2/src/plugins/Scrollbar.js

Lines 358 to 364 in 522e82b

	let position = this.state.isHorizontal
	? nativeEvent.offsetX ||
	nativeEvent.layerX ||
	this.getTouchX(nativeEvent)
	: nativeEvent.offsetY ||
	nativeEvent.layerY ||
	this.getTouchY(nativeEvent);

We should instead use the ?? operator for cases like this.

Motivation and Context

Fixes #723

How Has This Been Tested?

Tested on local examples

Types of changes

• 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:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.

[pradeepnschrodinger]

@karry08 , friendly ping

[karry08]

lgtm

[pradeepnschrodinger]

Released with v2.0.12.