workspace symbols: Default to empty Vec on None

A language server might send None as the response to workspace symbols.
We should treat this as the empty Vec rather than the server sending
an error status. This fixes the interaction with gopls which uses
None to mean no matching symbols.

helix-term/src/commands/lsp.rs

@@ -386,10 +386,7 @@ pub fn workspace_symbol_picker(cx: &mut Context) {
     cx.callback(
         future,
         move |_editor, compositor, response: Option<Vec<lsp::SymbolInformation>>| {
-            let symbols = match response {
-                Some(s) => s,
-                None => return,
-            };
+            let symbols = response.unwrap_or_default();
             let picker = sym_picker(symbols, current_url, offset_encoding);
             let get_symbols = |query: String, editor: &mut Editor| {
                 let doc = doc!(editor);
@@ -420,9 +417,7 @@ pub fn workspace_symbol_picker(cx: &mut Context) {
                     let response: Option<Vec<lsp::SymbolInformation>> =
                         serde_json::from_value(json)?;
 
-                    response.ok_or_else(|| {
-                        anyhow::anyhow!("No response for workspace symbols from language server")
-                    })
+                    Ok(response.unwrap_or_default())
                 };
                 future.boxed()
             };