Fix index out of range issue.

In the case buffer is deleted, `getbufline` returns empty array.

autoload/LSP.vim

@@ -6,7 +6,7 @@ function! LSP#text(...) abort
     let l:buf = get(a:000, 0, '')
 
     let l:lines = getbufline(l:buf, 1, '$')
-    if l:lines[-1] !=# '' && &fixendofline
+    if len(l:lines) > 0 && l:lines[-1] !=# '' && &fixendofline
         let l:lines += ['']
     endif
     return l:lines

src/language_server_protocol.rs

@@ -1833,17 +1833,15 @@ impl LanguageClient {
 
     pub fn textDocument_didChange(&self, params: &Value) -> Fallible<()> {
         info!("Begin {}", lsp::notification::DidChangeTextDocument::METHOD);
-        let (bufnr, languageId, filename): (u64, String, String) = self.gather_args(
-            &[VimVar::Bufnr, VimVar::LanguageId, VimVar::Filename],
-            params,
-        )?;
+        let (languageId, filename): (String, String) =
+            self.gather_args(&[VimVar::LanguageId, VimVar::Filename], params)?;
         if !self.get(|state| state.text_documents.contains_key(&filename))? {
             info!("Not opened yet. Switching to didOpen.");
             return self.textDocument_didOpen(params);
         }
 
         let (text,): (Vec<String>,) =
-            self.gather_args(&[format!("LSP#text({})", bufnr)], params)?;
+            self.gather_args(&[format!("LSP#text('{}')", filename)], params)?;
 
         let text = text.join("\n");
         let text_state = self.get(|state| {

src/types.rs

@@ -179,7 +179,9 @@ impl State {
         Ok(State {
             tx,
 
-            clients: HashMap::new(),
+            clients: hashmap! {
+                None => client.clone(),
+            },
 
             vim: Vim::new(client),