fix: handle empty/failed response for UPI and card payment

Author: Mishra-coder

frontend/src/components/Checkout.jsx

@@ -42,7 +42,15 @@ const Checkout = ({ cartItems, onClose, onOrderPlaced }) => {
         headers: { 'Content-Type': 'application/json' },
         body: JSON.stringify({ amount: totalAmount }),
       });
-      const data = await res.json();
+
+      if (!res.ok) {
+        const errText = await res.text();
+        throw new Error(`Server error ${res.status}: ${errText || 'No response from server'}`);
+      }
+
+      const text = await res.text();
+      if (!text) throw new Error('Empty response from payment server. Make sure the backend is running and VITE_API_URL is set correctly.');
+      const data = JSON.parse(text);
 
       const options = {
         key: import.meta.env.VITE_RAZORPAY_KEY_ID,
@@ -57,7 +65,9 @@ const Checkout = ({ cartItems, onClose, onOrderPlaced }) => {
             headers: { 'Content-Type': 'application/json' },
             body: JSON.stringify(response),
           });
-          const verifyData = await verifyRes.json();
+          const verifyText = await verifyRes.text();
+          if (!verifyText) { alert('Payment verification failed: empty response from server.'); return; }
+          const verifyData = JSON.parse(verifyText);
           if (verifyData.success) {
             if (onOrderPlaced) onOrderPlaced(cartItems);
             setOrderPlaced(true);