fix: check for column content before replacing

lib/workers/pr/body/updates-table.ts

@@ -62,8 +62,8 @@ export function getPrUpdatesTable(config: BranchConfig): string {
     let val = '|';
     for (const column of tableColumns) {
       const content = row[column]
-        .replace(/^@/, '@​')
-        .replace(/\|/g, '\\|');
+        ? row[column].replace(/^@/, '@​').replace(/\|/g, '\\|')
+        : '';
       val += ` ${content} |`;
     }
     val += '\n';