Cancelling opening a database does not work

[negasora]

Version and Platform (required):

• Binary Ninja Version: 5.4.9506-dev

Bug Description:
When you cancel opening a database in the progress dialog, the database is still opened, just with a few cancellation messages in the log

Steps To Reproduce:
Please provide all steps required to reproduce the behavior:

1. Open any database large enough to trigger the progress dialog
2. Click Cancel
3. Notice the database is opened anyway

Expected Behavior:
Cancelling opening the database should not result in the database being opened