Report Widgets Core: Fix collapse button border

What does this MR do and why?

This MR fixes the collapse button border showing when the button is hidden.

The border should not show when the extension is loading or errored.

Screenshots or screen recordings

Before

After

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #345497 (closed)