Add 404 support

urlforward/views.py

-from django.shortcuts import render, redirect
+from django.shortcuts import render, redirect, get_object_or_404
 
 from .models import Url
 
@@ -11,13 +11,13 @@ def index(request):
     return render(request, 'index.html', context)
 
 def redir(request, url_id):
-    u = Url.objects.get(id=url_id)
+    u = get_object_or_404(Url, id=url_id)
     u.used += 1
     u.save()
     return redirect(u.target)
 
 def details(request, url_id):
     context = {
-        'url': Url.objects.get(id=url_id)
+        'url': get_object_or_404(Url, id=url_id)
     }
     return render(request, 'details.html', context)