[Feature Request] When close last editor tab, create a new untitled empty tab instead

**Is your feature request related to a problem? Please describe.**

Currently, the visualizer does not allow to close the last tab. This is ok, but will pose additional layer of complexity on user operation.

**Describe the solution you'd like**

When close last editor tab, create a new untitled empty tab instead.

**Describe alternatives you've considered**


**Additional context**

