If the size of item is 0, EstimateSize will be used as a fallback.

[baco16g]

Describe

• Consider a pattern in which an item component does not render content under certain conditions.
  • For example, in a list that renders only text, an empty string height is 0.
• In the short circuit evaluation below, EstimateSize is used as the offset value, even if I purposely set the size to 0.

vue-virtual-scroll-list/src/virtual.js

Lines 220 to 224 in 095a5d5

	for (let index = 0; index < givenIndex; index++) {
	// this.__getIndexOffsetCalls++
	indexSize = this.sizes.get(this.param.uniqueIds[index])
	offset = offset + (indexSize || this.getEstimateSize())
	}

To Reproduce

Steps to reproduce the behavior:

1. Scroll down to index 10. Although it is a buffer value, range does not change.
2. Scroll down to index 14. The range has finally changed, but the padFront value seems to be incorrect.

Reproduce demo

• I only set height to 0 for items with even indices.
• https://codesandbox.io/s/live-demo-virtual-list-dulih

Other

• Version 2.2.0
• Browser chrome, safari

[tangbc]

This scene is so special but need fix.

[tangbc]

New version 2.2.1 fix it.