Keybindings reset on invalid command

[rpeshkov]

Describe the bug
If there was a typo in keybinding command, all keybindings get erased. Only togglevim command helps to restore it back.

To Reproduce
Steps to reproduce the behavior:

1. Open settings.json
2. Add keybindings for normal mode:

    "vim.normalModeKeyBindingsNonRecursive": [
        {
            "before": ["<C-d>"],
            "commands": [ "cursorPageDown" ]
        },
        {
            "before": ["<C-u>"],
            "commands": [ "abracadabra_not_existing_command" ]
        }
    ]

3. Press Ctrl+d to see that it works
4. Press Ctrl+u - nothing happens, because command doesn't exist.
5. Press Ctrl+d once again - it doesn't work now.

Expected behavior
In provided example - after pushing Ctrl+u that triggers not existing command, Ctrl+d should continue to work.

Environment (please complete the following information):

• Extension (VsCodeVim) version: 0.17.0
• VSCode version: 1.30.1
• OS: MacOS 10.14.2 (18C54)

[rpeshkov]

Additional note. This happens only for normalModeKeyBindingsNonRecursive bindings. normalModeKeyBindings don't have this issue.