fix issue caused by malformed urls

Entering a malformed URL would cause a submission draft failure. This
was because of an error that was raised during url validation that we
weren't handling correctly. Adding the appropriate rescue for errors on
validation fixes this issue.

Test Plan
- Create an assignment with an online_url submission type
- Navigate to the assignment as the student
- Enter a malformed url e.g. http:www.google.com
- The draft should be created but there should be a warning below the
  input stating that a valid url should be entered and there should be
  no submit button
- Enter a valid url and note that the draft should be saved and the
  submit button should be displayed.
- Enter a malformed url again and the draft should be saved and the
  submit button should disappear. There should also be a warning message
  about entering a valid url below the input.

fixes WOKE-40
fixes WOKE-41
flag=assignments_2_student

Change-Id: I64d017188e8e48cd9851139f2a7e1a7dfad63647
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/215803
Tested-by: Jenkins
Reviewed-by: Steven Burnett <[email protected]>
QA-Review: Steven Burnett <[email protected]>
Product-Review: Steven Burnett <[email protected]>

app/models/submission_draft.rb

@@ -39,7 +39,7 @@ def validate_url
         # otherwise leaves the url as whatever the user submitted as thier draft
         value, = CanvasHttp.validate_url(self.url)
         self.send("url=", value)
-      rescue URI::Error, ArgumentError
+      rescue
         return
       end
     end
@@ -80,7 +80,7 @@ def meets_url_criteria?
     begin
       CanvasHttp.validate_url(self.url)
       true
-    rescue URI::Error, ArgumentError
+    rescue
       false
     end
   end

spec/models/submission_draft_spec.rb

@@ -197,6 +197,11 @@
         expect(@submission_draft.meets_assignment_criteria?).to eq(false)
       end
 
+      it 'returns false if the url is malformed' do
+        @submission_draft.url = 'http:www.google.com'
+        expect(@submission_draft.meets_assignment_criteria?).to eq(false)
+      end
+
       it 'returns false if the url is empty' do
         @submission_draft.url = ''
         expect(@submission_draft.meets_assignment_criteria?).to eq(false)