I apologize for not knowing English!
steps for repeat:

1. open tabs (1 or more) in the first workspace
2. open tabs (1 or more) in the second workspace
3. select first workspace
4. close tabs
5. opera automatically switch to second workspace and show alert about will be close tabs
6. if press button yes == close browser
7. if press button no -> close alert -> close active tab
8. close 1 any another tab (with more inactive tabs) -> close browser
   unlisted screen animation on youtube