`workbench.action.openEditorAtIndex1` broken in Vim mode

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Is this a BUG REPORT or FEATURE REQUEST? (choose one):

Environment:

• VSCode Version: 1.11.2
• VsCodeVim Version: 0.6.20
• OS: Ubuntu Linux

What happened:

I bind key sequence [B (uppercase) to go for first opened tab, then I pressed this combination and the editor (editable area) stuck.

I went to dev tools and found this:

shell.ts:475 Converting circular structure to JSON: TypeError: Converting circular structure to JSON
    at Object.i [as stringify] (file:////usr/share/code/resources/app/out/vs/workbench/electron-browser/workbench.main.js:28:41110)
    at Function.e.replyOK (file:////usr/share/code/resources/app/out/vs/workbench/electron-browser/workbench.main.js:28:758999)
    at file:////usr/share/code/resources/app/out/vs/workbench/electron-browser/workbench.main.js:28:758514
    at Object.g [as _notify] (file:////usr/share/code/resources/app/out/vs/workbench/electron-browser/workbench.main.js:28:50313)
    at Object.enter (file:////usr/share/code/resources/app/out/vs/workbench/electron-browser/workbench.main.js:28:53887)
    at _run (file:////usr/share/code/resources/app/out/vs/workbench/electron-browser/workbench.main.js:28:55715)
    at _completed (file:////usr/share/code/resources/app/out/vs/workbench/electron-browser/workbench.main.js:28:55156)
    at then (file:////usr/share/code/resources/app/out/vs/workbench/electron-browser/workbench.main.js:28:57148)
    at Object.enter (file:////usr/share/code/resources/app/out/vs/workbench/electron-browser/workbench.main.js:28:52966)
    at _run (file:////usr/share/code/resources/app/out/vs/workbench/electron-browser/workbench.main.js:28:55715)e.onUnexpectedError @ shell.ts:475(anonymous function) @ shell.ts:435e.onUnexpectedError @ errors.ts:68o @ errors.ts:88(anonymous function) @ winjs.base.js:41(anonymous function) @ winjs.base.js:38
winjs.base.js:45 WARNING: Promise with no error callback:107
winjs.base.js:46 Object {exception: TypeError: Converting circular structure to JSON
    at Object.i [as stringify] (file:////usr/share/…, error: null, promise: n.C…s.d…e._creator, handler: undefined, id: 107…}
winjs.base.js:48 TypeError: Converting circular structure to JSON
    at Object.i [as stringify] (marshalling.ts:10)
    at Function.e.replyOK (ipcRemoteCom.ts:32)
    at ipcRemoteCom.ts:235
    at Object.g [as _notify] (winjs.base.raw.js:1170)
    at Object.enter (winjs.base.raw.js:852)
    at _run (winjs.base.raw.js:1068)
    at _completed (winjs.base.raw.js:1036)
    at then (winjs.base.raw.js:1566)
    at Object.enter (winjs.base.raw.js:747)
    at _run (winjs.base.raw.js:1068)

What did you expect to happen:
Go to first opened tab.

How to reproduce it:

1. define those keys in settings.json:

{
        "vim.otherModesKeyBindingsNonRecursive": [
        {
            "before": ["[", "b"],
            "after": [],
            "commands": [
                {
                    "command": "workbench.action.previousEditor"
                }
            ]
        },
        {
            "before": ["]", "b"],
            "after": [],
            "commands": [
                {
                    "command": "workbench.action.nextEditor"
                }
            ]
        },
        {
            "before": ["[", "B"],
            "after": [],
            "commands": [
                {
                    "command": "workbench.action.openEditorAtIndex1"
                }
            ]
        },
        {
            "before": ["]", "B"],
            "after": [],
            "commands": [
                {
                    "command": "workbench.action.openLastEditorInGroup"
                }
            ]
        }]
}

2. Navigate to first tab using [B (uppercase)
3. see the error in dev-tools.

If you bind another command on this shortcut it works fine.
If you do navigate using default shortcut alt+1 then it works okay.
So I blame Vim plugin on this.

Reproduce the issue using the settings.json keybindings and the [B] sequence, then compare it with the default alt+1 shortcut and inspect the VS Code developer-tools error. Trace how the Vim binding invokes workbench.action.openEditorAtIndex1; done means the first opened tab is selected without the circular-structure error or a stuck editor.