Crash caused by mapping

Crash
VSCode stops responding

To Reproduce

1. Add following mapping to settings.json:

    "vim.normalModeKeyBindingsNonRecursive": [
        {
            "before": ["n"],
            "commands": ["search.action.focusNextSearchResult"]
        }
    ]

2. Open any text file
3. Ensure that there is no search results. Press "Clear search results button" button on search panel if necessary
4. Focus opened file
5. Press n (the key used in step 1)
6. See VSCode stops responding to any clicks and key presses

Expected behavior
There is no any concrete expected behavior because search.action.focusNextSearchResult action is meaningless until search is performed, but at least VSCode is not expected to crash

Screenshots

Environment:
"Developers: Show Running Extensions" -> "Report Issue":

{
	"messages": [],
	"activationTimes": {
		"startup": true,
		"codeLoadingTime": 519,
		"activateCallTime": 1,
		"activateResolvedTime": 127,
		"activationEvent": "*"
	},
	"runtimeErrors": []
}

• Issue Type: Bug
• Extension Name: vim
• Extension Version: 1.8.0
• OS Version: Darwin x64 17.6.0
• VSCode version: 1.34.0

Reproduce the crash in VSCodeVim by adding the mapping in settings.json, opening a text file with no search results, and pressing n. Start by tracing the vim extension's handling of the search.action.focusNextSearchResult command. Done means the command no longer makes VSCode stop responding when no search has been performed.