VSIX Installer gives error "Object reference not set to an instance of an object."

Question

As the title says, whenever I try to install an extension for Visual Studio 2019 the VSIX Installer gives the error message: Object reference not set to an instance of an object. I found some similar posts but nothing that was quite like what's happening here. I've tried deleting certain folders in Appdata/Local, tried running devenv /resetuserdata in the console. Although nothing seems to work, so I was curious if anybody else has had this issue and any ideas on how to possibly fix it?

Picture of VSIX with Error Message

Install Log:

1/11/2021 12:59:18 PM - -------------------------------------------
1/11/2021 12:59:18 PM - vsixinstaller.exe version:
1/11/2021 12:59:18 PM - 16.8.3036
1/11/2021 12:59:18 PM - -------------------------------------------
1/11/2021 12:59:18 PM - Command line parameters:
1/11/2021 12:59:18 PM - C:\Program Files (x86)\Microsoft Visual Studio\Installer\resources\app\ServiceHub\Services\Microsoft.VisualStudio.Setup.Service\vsixinstaller.exe,/appidinstallpath:F:\VSCODEIDE\Common7\IDE\devenv.exe,/skuName:Community,/skuVersion:16.8.30804.86,/appidname:Microsoft Visual Studio Community 2019,/culture:en-US,/noep,C:\Users\xxxxxxx\AppData\Local\Temp\VSIXpg4jcyqq.vsix
1/11/2021 12:59:18 PM - -------------------------------------------
1/11/2021 12:59:18 PM - Microsoft VSIX Installer
1/11/2021 12:59:18 PM - -------------------------------------------
1/11/2021 12:59:18 PM - System.NullReferenceException: Object reference not set to an instance of an object.
   at VSIXInstaller.SetupExtensions.GetLaunchableInstances(IQuery query)
   at VSIXInstaller.SupportedSKUs.EnumerateIsolatedInstalls(Action`1 callback)
   at VSIXInstaller.SupportedSKUs.AddInstalledLocationBasedSKUs(IntPtr userToken)
   at VSIXInstaller.SupportedSKUs.InitializeSupportedSKUs(IntPtr userToken)
   at VSIXInstaller.ExtensionService.InitializeSupportedSKUs(ICommandLineData cmdLineData, IntPtr duplicatedUserToken)
   at VSIXInstaller.App.Initialize(Boolean isRepairSupported)
   at VSIXInstaller.App.Initialize()
   at System.Threading.Tasks.Task`1.InnerInvoke()
   at System.Threading.Tasks.Task.Execute()
--- End of stack trace from previous location where exception was thrown ---
   at Microsoft.VisualStudio.Telemetry.WindowsErrorReporting.WatsonReport.GetClrWatsonExceptionInfo(Exception exceptionObject)

Answer 1

To add an answer here for more community members handle similar issues.

Thanks to ErikEJ for sharing the solution.

Since your VS has broken, you could repair vs from vs_installer that actually solves your issue.