[Bug][DropDownList] When items are added dynamically and the popup should open upwards, there is extra space between the popup and the component

[kdikov82]

Describe the bug A clear and concise description of what the bug is.

To Reproduce Open the following example (tested with version 4.0.0):

• https://codesandbox.io/s/elated-resonance-yxqzcj?file=/src/main.vue

Scroll down to the second DropDownList and click on it to open the popup. The popup is offset.

The correct position is calculated if you scroll up and down the main scrollbar.

The issue is due to an initial calculation of the offset based on the no data content "min-height".