## Description
<!-- Describe the big picture of your changes to communicate to the
maintainers
why we should accept this pull request. -->
In my config I use the following flag to disable the default
`MatchParen` plugin.
```
vim.g.loaded_matchparen = 1
```
This causes an error when `bigfile` tries to call the `NoMatchParen`
command since it does not exist.
This PR fixes that by checking for the existence of the command before
executing it.
## Related Issue(s)
<!--
If this PR fixes any issues, please link to the issue here.
- Fixes #<issue_number>
-->
## Screenshots
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