Crash when dragging the tab

When I'm dragging from a window with only one tab, the app crashes.

When I'm dragging from a window with two or more tab to a new window (after dropping the first), the app doesn't crash. The app doesn't crash also when I drag all the remaining tab(s) to the new window.
However, when I drag the tab one by one back to the original window, when the new window has only one tab remaining and I drag the last one back to the original window, the app crashes.

Anyone has the same problem?

Textastic is my favorite code editor, but I can only use others instead for a little while......