Use more pythonic way of checking whether list is empty

Issue: HIC-170
Change-Id: I7dbcd429aeacb194e5420ed71b6eb371f67d99d6
diff --git a/crashreport_stats/views.py b/crashreport_stats/views.py
index d9bab4e..58e3261 100644
--- a/crashreport_stats/views.py
+++ b/crashreport_stats/views.py
@@ -68,7 +68,7 @@
                         + "?uuid="
                         + devices[0].uuid
                     )
-                if len(devices) == 0:
+                if not devices:
                     messages.warning(request, "No devices found.")
             else:
                 return HttpResponseRedirect(