Remove extra empty space for files when file icons are turned off (#16142)

Closes #16073

<img width="269" alt="image" src="https://github.com/user-attachments/assets/88b7ff9f-17ec-4764-b37a-c218d7ad14ec">

Release Notes:

- Removed extra empty space for files when file icons are turned off ([#16073](https://github.com/zed-industries/zed/issues/16073))

crates/project_panel/src/project_panel.rs

@@ -2120,13 +2120,12 @@ impl ProjectPanel {
                                 .into_any_element(),
                         )
                     })
-                    .child(if let Some(icon) = &icon {
+                    .when_some(icon, |this, icon| {
-                        h_flex().child(Icon::from_path(icon.to_string()).color(filename_text_color))
+                        this.child(
-                    } else {
+                            h_flex().child(
-                        h_flex()
+                                Icon::from_path(icon.to_string()).color(filename_text_color),
-                            .size(IconSize::default().rems())
+                            ),
-                            .invisible()
+                        )
-                            .flex_none()
                     })
                     .child(
                         if let (Some(editor), true) = (Some(&self.filename_editor), show_editor) {