Fixes https://github.com/zed-industries/zed/issues/9340 The flickering was caused by the pane trying to restore focus on a `FocusHandle` that wasn't being rendered anymore. This commit uses the new `WeakFocusHandle` to avoid retaining a reference to focus handles that don't exist anymore. Release Notes: - Fixed a bug that caused flickering when interacting with the language server logs ([#9340](https://github.com/zed-industries/zed/issues/9340)).