Not all resources are released on window close

[Kindrat]

Describe the bug
On window close client process continue working making it zombie.

To Reproduce
Steps to reproduce the behavior:

1. Connect to any cassandra node
2. Close window
3. Check process PID still exists

Expected behavior
Process should release all resources and gracefully shut down.

Desktop (please complete the following information):

• OS: Windows
• Version 10