Ensure suggestion works for number text

Issue: https://gitlab.com/gitlab-org/gitlab/-/issues/224143

app/assets/javascripts/lib/utils/text_markdown.js

@@ -166,6 +166,7 @@ export function insertMarkdownText({
   let editorSelectionEnd;
   let lastNewLine;
   let textToInsert;
+  selected = selected.toString();
 
   if (editor) {
     const selectionRange = getEditorSelectionRange(editor);

changelogs/unreleased/224143-suggestion-button-not-work-for-numbers.yml

+---
+title: Ensure suggestion works for number text
+merge_request: 44332
+author:
+type: fixed

spec/frontend/lib/utils/text_markdown_spec.js

@@ -13,6 +13,23 @@ describe('init markdown', () => {
     textArea.parentNode.removeChild(textArea);
   });
 
+  describe('insertMarkdownText', () => {
+    it('will not error if selected text is a number', () => {
+      const selected = 2;
+
+      insertMarkdownText({
+        textArea,
+        text: '',
+        tag: '',
+        blockTag: null,
+        selected,
+        wrap: false,
+      });
+
+      expect(textArea.value).toBe(selected.toString());
+    });
+  });
+
   describe('textArea', () => {
     describe('without selection', () => {
       it('inserts the tag on an empty line', () => {