pinning tabs when a window has been closed results in error

[petemill]

Description

pinning tabs when a window has been closed results in error 'Object has been destroyed'

Steps to Reproduce

1. Start browser (clean profile)
2. Open some tabs
3. Open a new window (ctrlorcmd-n)
4. Close newly opened window (ctwlorcmd-w)
5. Pin one of the tabs in the original window

Actual result:
Error:

An uncaught exception occurred in the main process Uncaught Exception:
Error: Object has been destroyed
    at updatePinnedTabs (/Users/petemill/Development/Brave/browser-laptop/app/browser/windows.js:76:11)
    at Immediate.setImmediate (/Users/petemill/Development/Brave/browser-laptop/app/browser/windows.js:244:11)
    at runCallback (timers.js:672:20)
    at tryOnImmediate (timers.js:645:5)
    at processImmediate [as _immediateCallback] (timers.js:617:5)

Expected result:
No error

Reproduces how often:

Brave Version

about:brave info:
master

Reproducible on current live release:
0.19 pinned tab code is different - does not have many of the fixes in 0.20 / master