git_ui: Fix double borrow when showing worktree error message (#54555)

Fixes ZED-6Q0

Self-Review Checklist:

- [x] I've reviewed my own diff for quality, security, and reliability
- [x] Unsafe blocks (if any) have justifying comments
- [x] The content is consistent with the [UI/UX
checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
- [ ] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable

Closes #54544

Release Notes:

- Fixed a crash that could occur when git worktree creating fails

crates/git_ui/src/git_panel.rs

@@ -6572,25 +6572,27 @@ pub(crate) fn show_error_toast(
         .is_some()
     { // Hide the cancelled by user message
     } else {
-        workspace.update(cx, |workspace, cx| {
-            let workspace_weak = cx.weak_entity();
-            let toast = StatusToast::new(format!("git {} failed", action), cx, |this, _cx| {
-                this.icon(
-                    Icon::new(IconName::XCircle)
-                        .size(IconSize::Small)
-                        .color(Color::Error),
-                )
-                .action("View Log", move |window, cx| {
-                    let message = message.clone();
-                    let action = action.clone();
-                    workspace_weak
-                        .update(cx, move |workspace, cx| {
-                            open_output(action, workspace, &message, window, cx)
-                        })
-                        .ok();
-                })
+        cx.defer(move |cx| {
+            workspace.update(cx, |workspace, cx| {
+                let workspace_weak = cx.weak_entity();
+                let toast = StatusToast::new(format!("git {} failed", action), cx, |this, _cx| {
+                    this.icon(
+                        Icon::new(IconName::XCircle)
+                            .size(IconSize::Small)
+                            .color(Color::Error),
+                    )
+                    .action("View Log", move |window, cx| {
+                        let message = message.clone();
+                        let action = action.clone();
+                        workspace_weak
+                            .update(cx, move |workspace, cx| {
+                                open_output(action, workspace, &message, window, cx)
+                            })
+                            .ok();
+                    })
+                });
+                workspace.toggle_status_toast(toast, cx)
             });
-            workspace.toggle_status_toast(toast, cx)
         });
     }
 }