Steps to reproduce:

1. Open firefox Nightly, login to Gmail.
2. Perform a search and then click advanced search options.
3. Click create filter.
4. Check Apply the label, move to button for selecting a label, press it with space, and try to navigate in the newly opened menu.

Actual behavior:

Firefox Nightly crashes, the following is written in the NVDA log
ERROR - eventHandler.executeEvent (19:12:48.443):
error executing event: gainFocus on <NVDAObjects.IAccessible.mozilla.BrokenFocusedState object at 0x0531EBF0> with extra args of {}
Traceback (most recent call last):
File "eventHandler.pyc", line 155, in executeEvent
File "eventHandler.pyc", line 92, in init
File "eventHandler.pyc", line 100, in next
File "C:\Users\Lukasz\AppData\Roaming\nvda\addons\remote\globalPlugins\remoteClient_init_.py", line 426, in event_gainFocus
File "eventHandler.pyc", line 100, in next
File "appModules\firefox.pyc", line 24, in event_stateChange
File "eventHandler.pyc", line 100, in next
File "browseMode.pyc", line 1448, in event_gainFocus
File "textInfos\offsets.pyc", line 458, in expand
File "virtualBuffers_init_.pyc", line 376, in _getUnitOffsets
File "textInfos\offsets.pyc", line 437, in _getUnitOffsets
File "textInfos\offsets.pyc", line 306, in getCharacterOffsets
File "virtualBuffers_init.pyc", line 230, in _getTextRange
WindowsError: [Error 1726] remote invocation of a procedure failed.

the crash report from Nightly is here:
https://crash-stats.mozilla.org/report/index/7f8b7e21-9ef0-4e44-b758-8c0b30190323

Expected behavior:

The list of the labels should be navigable.

System configuration

NVDA installed/portable/running from source:

Installed

NVDA version:

NVDA version alpha-16941,e3b2e797

Windows version:

Windows 7 x64

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

Firefox Nightly 68.0a1 (2019-03-23) (64-bit)

Other information about your system:

With JAWS Nightly doesn't crash in this situation.

Other questions

Does the issue still occur after restarting your PC?

Yes

Have you tried any other versions of NVDA?

No
cc @jcsteh @MarcoZehe