fix sorting

src/components/generic/Table/index.tsx

@@ -34,8 +34,8 @@ export const Table = ({ headings, rows }: TableProps): JSX.Element => {
 
     // Custom comparison for 'Last Heard' column
     if (sortColumn === "Last Heard") {
-      const aTimestamp = a[columnIndex].props.timestamp;
-      const bTimestamp = b[columnIndex].props.timestamp;
+      const aTimestamp = a[columnIndex].props.timestamp ? a[columnIndex].props.timestamp : 0;
+      const bTimestamp = b[columnIndex].props.timestamp ? b[columnIndex].props.timestamp : 0;
 
       if (aTimestamp < bTimestamp) {
         return sortOrder === "asc" ? -1 : 1;