fix NPE when forgetting to specify related_assignment for a self-eval codereview
fix NPE when forgetting to specify related_assignment for a self-eval codereview

CodeGrade/bottlenose,CodeGrade/bottlenose,blerner/bottlenose,blerner/bottlenose,blerner/bottlenose,CodeGrade/bottlenose,blerner/bottlenose,CodeGrade/bottlenose,blerner/bottlenose,blerner/bottlenose,CodeGrade/bottlenose,CodeGrade/bottlenose,blerner/bottlenose,CodeGrade/bottlenose