Keybase GUI sometimes issues indefinite video wakelocks

Laptop (Surface Book 2) is not going to sleep. Keybase is on a different virtual desktop, is not the active window, and no animated gifs/emojis are currently in the backlog. There are, however, static picture attachments.

Windows 10

```log
PS C:\WINDOWS\system32> powercfg /REQUESTS
DISPLAY:
[PROCESS] \Device\HarddiskVolume3\Users\aelius\AppData\Local\Keybase\Gui\Keybase.exe
Video Wake Lock
```
```log
PS C:\WINDOWS\system32> Get-WindowsEdition -Online -Verbose
VERBOSE: Target Image Version 10.0.18363.959

Edition : Professional
```
aka Win10 Pro 1909

my log id: cd869633b184087c3e3b4a1c

Start by reproducing the Windows 10 sleep issue while Keybase GUI has static picture attachments, then run `powercfg /REQUESTS` and compare the result with log id cd869633b184087c3e3b4a1c. Done means Keybase.exe no longer holds an indefinite Video Wake Lock and the laptop can sleep.

Written by the indexing model from the issue text.