fix console warnings when viewing rubrics in a2

we should ensure we have no console warnings when we are viewing
rubrics as a student.

Test Plan:
* as a teacher, create an assignment with a rubric
* as a student in a2, submit to this assignment
* as a teacher, grade this assignment in the following ways:
** without using the rubric
** using the rubric with the points left blank
** using the rubric with only some points left blank
** with a comment added
** without a comment added
** with the total score set to 0
** with a description on the criterion
** without a description on the criterion

* as a student in these scenarios, you should not see any
  console warnings when viewing the rubric

fixes COMMS-2473

Change-Id: Ic869de3c1d98296232a6aedba9c2011379551a66
Reviewed-on: https://gerrit.instructure.com/211210
Reviewed-by: Landon Gilbert-Bland <lbland@instructure.com>
QA-Review: Landon Gilbert-Bland <lbland@instructure.com>
Tested-by: Jenkins
Product-Review: Ryan Norton <rnorton@instructure.com>

app/jsx/assignments_2/student/graphqlData/RubricAssessment.js

@@ -54,7 +54,7 @@ export const RubricAssessment = {
     }),
     data: arrayOf(RubricAssessmentRating.shape),
     rubricAssociation: RubricAssociation.shape,
-    score: number.isRequired
+    score: number
   })
 }
 

app/jsx/assignments_2/student/graphqlData/RubricAssessmentRating.js

@@ -36,7 +36,7 @@ export const RubricAssessmentRating = {
   `,
 
   shape: shape({
-    _id: string.isRequired,
+    _id: string,
     criterion: shape({
       id: string.isRequired
     }),
@@ -46,7 +46,7 @@ export const RubricAssessmentRating = {
     outcome: shape({
       id: string.isRequired
     }),
-    points: number.isRequired
+    points: number
   })
 }
 

app/jsx/rubrics/types.js

@@ -72,5 +72,5 @@ export const rubricAssociationShape = {
 
 export const rubricAssessmentShape = {
   data: PropTypes.arrayOf(PropTypes.shape(assessmentShape)).isRequired,
-  score: PropTypes.number.isRequired
+  score: PropTypes.number
 }