drag test helper division by 0

[Yelinz]

Describe the bug
drag test helper can produce a division by 0, which causes an error for triggerEvent because the value is Infinity

To Reproduce
Reproduction unsure, but only seems to happen in headless test mode.

Expected behavior
Avoid the division by 0

Additional context
The offending line

  const scale = clientHeight / (rect.bottom - rect.top);

https://github.com/adopted-ember-addons/ember-sortable/blob/master/addon/src/test-support/helpers/drag.js#L61