lsp: Don't panic if init fails

We correctly filter out the language server inside Document to ignore it
if the capabilities are missing, so this way it'll simply ignore the
errored out LSP rather than panicking.

helix-lsp/src/lib.rs

@@ -337,7 +337,10 @@ pub fn get(&mut self, language_config: &LanguageConfiguration) -> Result<Arc<Cli
                         })
                         .await;
 
-                    value.expect("failed to initialize capabilities");
+                    if let Err(e) = value {
+                        log::error!("failed to initialize language server: {}", e);
+                        return;
+                    }
 
                     // next up, notify<initialized>
                     _client