Bottom border does not behave well on resizing

[xelra]

When resizing the browser window, the bottom border does not behave well.

Steps to reproduce:

• Make the window smaller so that the dialog becomes scrollable
• Issue 1: The bottom border does not appear
• Scroll down a bit to make the bottom border appear
• Scroll up completely again. This time the bottom border shows
• Make the windows big so that the dialog isn't scrollable
• Issue 2: The bottom border does not disappear

The top border doesn't seem to have this issue.

I've tested this in Chrome.