fix null errors on conversation holder

Author: cloudchamb3r

web_src/js/features/repo-issue.ts

@@ -187,12 +187,12 @@ export function initRepoIssueCommentDelete() {
           const path = conversationHolder.getAttribute('data-path');
           const side = conversationHolder.getAttribute('data-side');
           const idx = conversationHolder.getAttribute('data-idx');
-          const lineType = conversationHolder.closest('tr').getAttribute('data-line-type');
+          const lineType = conversationHolder.closest('tr')?.getAttribute('data-line-type');
 
           if (lineType === 'same') {
-            document.querySelector(`[data-path="${path}"] .add-code-comment[data-idx="${idx}"]`).classList.remove('tw-invisible');
+            document.querySelector(`[data-path="${path}"] .add-code-comment[data-idx="${idx}"]`)?.classList.remove('tw-invisible');
           } else {
-            document.querySelector(`[data-path="${path}"] .add-code-comment[data-side="${side}"][data-idx="${idx}"]`).classList.remove('tw-invisible');
+            document.querySelector(`[data-path="${path}"] .add-code-comment[data-side="${side}"][data-idx="${idx}"]`)?.classList.remove('tw-invisible');
           }
 
           conversationHolder.remove();