Fix highlight errors when lsp crash or stop (#864)

* Fix highlight errors when lsp crash or stop

It adds a check wether the client is still available before
highlighting.

If the client is not there anymore it returns `true` to unregister the
autocommand

This fix the
`method textDocument/documentHighlight is not supported by any of the servers registered for the current buffer`
errors when doing a LspRestart or the server crashes

* Delete the highlight autocommands in the LspDetatch event

* Only delete autocmds for the current buffer with the group name

* Simplify clearing the autocommands

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Co-authored-by: Francis Belanger <francis.belanger@ubisoft.com>

0 files changed, 0 insertions, 0 deletions