robot prevention : check if human field present in object data

Signed-off-by: CapsLock <faimaison@legeox.net>

wifiwithme/apps/contribmap/decorators.py

@@ -14,7 +14,7 @@ def prevent_robots(field_name='human_field'):
         def _wrapped_func(request, *args, **kwargs):
             if request.method == 'POST':
                 form = PublicContribForm(request.POST)
-                if form.data[field_name]:
+                if field_name in form.data and form.data[field_name]:
                     return HttpResponseForbidden()
             return func(request, *args, **kwargs)
         return _wrapped_func