fix: empty xml file (#633)

* fix: empty xml file

* fix: test and change set

---------

Co-authored-by: Davis Voicescuks <davis.voicescuks@sap.com>

Author: marufrasully

.changeset/blue-needles-peel.md

@@ -0,0 +1,7 @@
+---
+"@ui5-language-assistant/language-server": patch
+"vscode-ui5-language-assistant": patch
+"@ui5-language-assistant/vscode-ui5-language-assistant-bas-ext": patch
+---
+
+No completion items for empty file

packages/language-server/src/completion-items.ts

@@ -42,6 +42,9 @@ export function getCompletionItems(opts: {
   const documentText = opts.document.getText();
   const { cst, tokenVector } = parse(documentText);
   const ast = buildAst(cst as DocumentCstNode, tokenVector);
+  if (!ast.rootElement) {
+    return [];
+  }
   const suggestions = getXMLViewCompletions({
     context: opts.context,
     offset: opts.document.offsetAt(opts.textDocumentPosition.position),

packages/language-server/test/unit/completion-items.test.ts

@@ -36,6 +36,12 @@ describe("the UI5 language assistant Code Completion Services", () => {
     appContext = getDefaultContext(ui5SemanticModel);
   });
 
+  it("no completion items for empty file - no error", () => {
+    const xmlSnippet = `⇶`;
+    const suggestions = getSuggestions(xmlSnippet, appContext);
+    expect(suggestions).toStrictEqual([]);
+  });
+
   it("will get completion values for UI5 property", () => {
     const xmlSnippet = `<mvc:View 
                           xmlns:mvc="sap.ui.core.mvc"