Bug Description:

Steps to Reproduce:

1. yarn & yarn browser build & yarn browser start.
2. Open http://localhost:3000/ and open any workspace.
3. Use alt + n to call NEW_FILE command some times, we can see tab named Untitled-${index} one by one. And we can notice the number in label is start from 0 rather then 1(vscode is started from 1).
4. Call NEW_FILE command again after close some older Untitled file, it should used the number which is closed just now like vscode.

Refer to the following screenshots:

vscode behavior:

theia behavior:

Additional Information

• Operating System: macos
• Theia Version: 1.26.0 the latest commit id is 0e05d0a