fix: improve pdf parsing with pdfjs-dist fallback

backend/src/receipt-parsing/receipt-parsing.service.ts

@@ -298,7 +298,9 @@ export class ReceiptParsingService {
         for (let i = 1; i <= pdfDocument.numPages; i++) {
           const page = await pdfDocument.getPage(i);
           const textContent = await page.getTextContent();
-          const pageText = textContent.items.map(item => item.str).join(' ');
+          const pageText = textContent.items
+            .map((item: any) => (item.str ? item.str : ''))
+            .join(' ');
           fullText += pageText + ' ';
         }