Follow-up to https://github.com/zed-industries/zed/pull/53778

Covers another case when opening a directory via the file picker _from a
blank project_

<img width="865" height="539" alt="image"
src="https://github.com/user-attachments/assets/43eb035b-4f0f-4e8c-bfa3-fbcd7b4beb13"
/>

resulted in 

<img width="1072" height="1162" alt="image"
src="https://github.com/user-attachments/assets/59c588b9-8925-41bb-b9fb-e4906c43c723"
/>


Release Notes:

- Fixed the sidebar opening when a new directory in a new window was
opened