Export Responses button throws a stack trace when the matching item has a distractor option

We believe that bug can be resolved by the patch attached in the Jira SAM-1480 by Brooke Biltimier.

Steps to reproduce the issue (please see attached images):

1. Instructor creates an assessment with a matching question which has a "distractor" option.
2. Instructor publishes the assessment.
3. The student takes the assessment.
4. The student answers the matching question by selecting the 'distractor' option.
5. The student submits the assessment.
6. Instructor tries to export the responses to an Excel file and that stack trace is displayed in the application logs:

java.lang.NullPointerException
at org.sakaiproject.tool.assessment.facade.AssessmentGradingFacadeQueries.getExportResponsesData(AssessmentGradingFacadeQueries.java:2352)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:317)