fix(frontend): guard against JSON.stringify returning undefined in result panel row mapping

Author: juliethecao

frontend/src/app/workspace/component/result-panel/result-panel-modal.component.ts

@@ -112,7 +112,7 @@ export class RowModalComponent implements OnChanges {
     rowData: Record<string, unknown>
   ): { key: string; value: string; mediaSrc: string; isVideo: boolean; isImage: boolean; isAudio: boolean }[] {
     return Object.entries(rowData).map(([key, val]) => {
-      const value = typeof val === "string" ? val : JSON.stringify(val);
+      const value = typeof val === "string" ? val : (JSON.stringify(val) ?? String(val));
       return {
         key,
         value,