Setting commands in remapping to a single object corrupts installation

Describe the bug
Adding an invalid command remapping breaks the extension. toggleVim command isn't found, no vim bindings work. After removing the setting, problem persists. The extension may be uninstalled, but reinstall fails. The extension must be manually deleted from the folder and reinstalled to fix

To Reproduce
Steps to reproduce the behavior:

0. Install Vim extension
1. set settings.json to

{
    "vim.normalModeKeyBindings": [
        {
            "before": [
                "b"
            ],
            "commands": {
                "command": "workbench.action.toggleTabsVisibility"
            }
        }
    ]
}

2. Reload

Expected behavior
Either key is remapped or visible error is shown and mapping is discarded

Extension functions after removal of invalid remapping

Screenshots
After adding the above settings file, even if it is removed afterwards, the following trace appears every launch

[2019-06-25 15:22:01.083] [renderer1] [error] remapping.commands is not iterable: TypeError: remapping.commands is not iterable
	at RemappingValidator.<anonymous> (C:\Users\brianbr\.vscode\extensions\vscodevim.vim-1.8.1\out\src\configuration\validators\remappingValidator.js:88:49)
	at Generator.next (<anonymous>)
	at __awaiter (C:\Users\brianbr\.vscode\extensions\vscodevim.vim-1.8.1\out\src\configuration\validators\remappingValidator.js:7:71)
	at new Promise (<anonymous>)
	at __awaiter (C:\Users\brianbr\.vscode\extensions\vscodevim.vim-1.8.1\out\src\configuration\validators\remappingValidator.js:3:12)
	at RemappingValidator.isRemappingValid (C:\Users\brianbr\.vscode\extensions\vscodevim.vim-1.8.1\out\src\configuration\validators\remappingValidator.js:67:16)
	at RemappingValidator.<anonymous> (C:\Users\brianbr\.vscode\extensions\vscodevim.vim-1.8.1\out\src\configuration\validators\remappingValidator.js:32:53)
	at Generator.next (<anonymous>)
	at __awaiter (C:\Users\brianbr\.vscode\extensions\vscodevim.vim-1.8.1\out\src\configuration\validators\remappingValidator.js:7:71)
	at new Promise (<anonymous>)
	at __awaiter (C:\Users\brianbr\.vscode\extensions\vscodevim.vim-1.8.1\out\src\configuration\validators\remappingValidator.js:3:12)
	at RemappingValidator.validate (C:\Users\brianbr\.vscode\extensions\vscodevim.vim-1.8.1\out\src\configuration\validators\remappingValidator.js:16:16)
	at ConfigurationValidator.<anonymous> (C:\Users\brianbr\.vscode\extensions\vscodevim.vim-1.8.1\out\src\configuration\configurationValidator.js:27:56)
	at Generator.next (<anonymous>)
	at fulfilled (C:\Users\brianbr\.vscode\extensions\vscodevim.vim-1.8.1\out\src\configuration\configurationValidator.js:4:58)

Environment (please complete the following information):

Extension (VsCodeVim) version: 1.8.1
VSCode version: Code 1.34.0 (a622c65b2c713c890fcf4fbf07cf34049d5fe758, 2019-05-15T21:59:37.030Z)
OS: Windows_NT x64 10.0.17134

Start with out/src/configuration/validators/remappingValidator.js at RemappingValidator.isRemappingValid and follow its call from configurationValidator.js. Reproduce the settings.json remapping, then verify that an invalid single-object commands value is rejected without breaking later launches or valid keybindings after the setting is removed.