don't run course link validator on questions in deleted banks

test plan:
* create a question bank
* create a question in the bank with an invalid link
* the course link validator should find it
* delete the question bank
* the course link validator should not flag the link
 in the question anymore

closes #CNVS-27389

Change-Id: Icab0298a071dc4c668ebbd0bfaab1e616e0c71af
Reviewed-on: https://gerrit.instructure.com/72677
Tested-by: Jenkins
Reviewed-by: Jeremy Stanley <jeremy@instructure.com>
QA-Review: Jahnavi Yetukuri <jyetukuri@instructure.com>
Product-Review: James Williams  <jamesw@instructure.com>

lib/course_link_validator.rb

@@ -52,6 +52,7 @@ class CourseLinkValidator
 
     # Assessment questions
     self.course.assessment_questions.active.each do |aq|
+      next if aq.assessment_question_bank.deleted?
       check_question(aq)
     end
     progress.update_completion! 15

spec/lib/course_link_validator_spec.rb

@@ -80,6 +80,30 @@ describe CourseLinkValidator do
 
   end
 
+  it "should not run on assessment questions in deleted banks" do
+    CourseLinkValidator.any_instance.stubs(:reachable_url?).returns(false) # don't actually ping the links for the specs
+    html = %{<a href='http://www.notarealsitebutitdoesntmattercauseimstubbingitanwyay.com'>linky</a>}
+
+    course
+    bank = @course.assessment_question_banks.create!(:title => 'bank')
+    aq = bank.assessment_questions.create!(:question_data => {'name' => 'test question',
+      'question_text' => html, 'answers' => [{'id' => 1}, {'id' => 2}]})
+
+    CourseLinkValidator.queue_course(@course)
+    run_jobs
+
+    issues = CourseLinkValidator.current_progress(@course).results[:issues]
+    expect(issues.count).to eq 1
+
+    bank.destroy
+
+    CourseLinkValidator.queue_course(@course)
+    run_jobs
+
+    issues = CourseLinkValidator.current_progress(@course).results[:issues]
+    expect(issues).to be_empty
+  end
+
   it "should not care if it can reach it" do
     CourseLinkValidator.any_instance.stubs(:reachable_url?).returns(true)