Steps to reproduce:

1. Start NVDA.
2. Open Python console then type:

 config.conf['UIA']['enabled'] = False

3. Restart NVDA.

Actual behavior:

NVDA can no longer be used. Error sound is played almost constantly.
Each error entry in the log ends in the following:
File "NVDAObjects\UIA_init_.py", line 739, in
class UIA(Window):
File "NVDAObjects\UIA_init_.py", line 1492, in UIA
def event_UIA_notification(self, notificationKind=None, notificationProcessing=UIAHandler.NotificationProcessing_CurrentThenMostRecent, displayString=None, activityId=None):
AttributeError: module 'UIAHandler' has no attribute 'NotificationProcessing_CurrentThenMostRecent'

Expected behavior:

As long as this config option exists it should work.

System configuration

NVDA installed/portable/running from source:

Running from source.

NVDA version:

Current master

Windows version:

Windows 7 x64

Name and version of other software in use when reproducing the issue:

None

Other information about your system:

Other questions

Does the issue still occur after restarting your PC?

Yes

Have you tried any other versions of NVDA? If so, please report their behaviors.

The same behavior exists on installed 2019.2.1 beta 1