Fix Stimulus validation: show all field errors, not just first one

Changed 'else if' to 'if' so both Author and Text validation errors
display when both fields are empty. Removed unreachable else block.

Fixes 4 failing Stimulus/Turbo RSpec tests.

Author: justin808

client/app/controllers/comments_controller.js

@@ -22,10 +22,8 @@ export default class extends Controller {
       errorList.innerHTML = '';
       if (!inputAuthor.value) {
         errors.push('Author');
-      } else if (!inputText.value) {
-        errors.push('Text');
-      } else {
-        errors.push('Author');
+      }
+      if (!inputText.value) {
         errors.push('Text');
       }
       errors.forEach((error) => {