Issue Id: e384fcb9-be29-b045-bd2f-efd4c2e60a5d

Versions
- 1.8.1
Stack
TypeError: Cannot read property 'gallery' of null
/vs/workbench/parts/extensions/node/extensionsWorkbenchService.ts#L576:16 (gallery)
/vs/base/common/callbackList.ts#L63:26 (apply)
/vs/base/common/event.ts#L117:26 (call)
/vs/base/parts/ipc/common/ipc.ts#L493:42 (fire)
vs/workbench/electron-browser/vs/base/common/winjs.base.raw.js#L1244:0 (onProgress)
vs/workbench/electron-browser/vs/base/common/winjs.base.raw.js#L1045:0 (_progress)
vs/workbench/electron-browser/vs/base/common/winjs.base.raw.js#L1244:0 (onProgress)
vs/workbench/electron-browser/vs/base/common/winjs.base.raw.js#L1045:0 (_progress)
vs/workbench/electron-browser/vs/base/common/winjs.base.raw.js#L1244:0 (onProgress)
vs/workbench/electron-browser/vs/base/common/winjs.base.raw.js#L1045:0 (_progress)