fix: Resolve QR code generation errors in ticket PDF creation

- Add validation in TicketPdfGenerator to ensure QR code data integrity
- Use compact() to remove nil values from QR code data hash
- Add error handling in Ticket#generate_qr_code with fallback generation
- Validate QR code data before passing to RQRCode library
- Add proper error logging for QR code generation failures
- Prevent "data must be a String, QRSegment, or an Array" errors

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

app/services/ticket_pdf_generator.rb

@@ -63,12 +63,22 @@ class TicketPdfGenerator
       pdf.text "Ticket QR Code", align: :center
       pdf.move_down 10
 
+      # Ensure all required data is present before generating QR code
+      if ticket.qr_code.blank?
+        raise "Ticket QR code is missing"
+      end
+
       qr_code_data = {
         ticket_id: ticket.id,
         qr_code: ticket.qr_code,
-        event_id: ticket.event.id,
-        user_id: ticket.user.id
-      }.to_json
+        event_id: ticket.event&.id,
+        user_id: ticket.user&.id
+      }.compact.to_json
+
+      # Validate QR code data before creating QR code
+      if qr_code_data.blank? || qr_code_data == "{}"
+        raise "QR code data is empty or invalid"
+      end
 
       qrcode = RQRCode::QRCode.new(qr_code_data)
       pdf.print_qr_code(qrcode, extent: 120, align: :center)