don't return an error to respondus when no quizzes are found

maybe this will fix the issue with importing into empty courses

refs #LA-750

Change-Id: Ie45ccabfed1f4838c88a6d23e3a42c35d58d00e2
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/235403
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
QA-Review: Clint Furse <cfurse@instructure.com>
Product-Review: James Williams <jamesw@instructure.com>
Reviewed-by: Jeremy Stanley <jeremy@instructure.com>

gems/plugins/respondus_soap_endpoint/lib/respondus_soap_endpoint/urn_RespondusAPIServant.rb

@@ -259,7 +259,7 @@ Implemented for: Canvas LMS}]
     else
       raise OtherError, "Invalid item type"
     end
-    raise(OtherError, "No items found") if list.item.empty?
+    raise(OtherError, "No items found") if list.item.empty? && !["quiz", "qdb"].include?(itemType)
     return [list]
   end