Outline is not refreshed after open a new file

[xianpul]

Describe the bug
New opened file is not outlined automatically, and outline panel view is not cleared after close all open files.

To Reproduce
Steps to reproduce the behavior of no outline after open a file:

1. Open a new file from "explorer" panel, then go to "outline-map" panel
2. There's no outline shown
3. Click any other panels, then go back to "outline-map". Outline is shown.

Steps to reproduce the behavior of outline not cleared:

1. Open two or more files from "explorer" panel, then go to "outline-map" panel
2. Switch to another panel, then go back to "outline-map" to trigger outline shown
3. Close all open editors, outline is still shown

Steps to reproduce the behavior of no expansion for a new opened file:

1. Open a Java file from "explorer" panel, then go to "outline-map" panel
2. Switch to another panel, then go back to "outline-map" to trigger outline shown
3. Move cursor to any method of Java class, the class was not expanded so the outline is blank due to following cursor feature.

Expected behavior
Outline should be displayed correctly

Screenshots

Desktop (please complete the following information):

• OS: MacOS
• Browser: Edge
• Version 13.2

Outline Map version: v1.0.1
VS code version: v1.79

Additional context
Add any other context about the problem here.