Fix for displaying left side comments when no discussion available

app/assets/javascripts/diffs/components/parallel_diff_comment_row.vue

@@ -57,7 +57,9 @@ export default {
       );
     },
     showRightSideCommentForm() {
-      return this.line.right.type && this.diffLineCommentForms[this.rightLineCode];
+      return (
+        this.line.right && this.line.right.type && this.diffLineCommentForms[this.rightLineCode]
+      );
     },
     className() {
       return (this.left && this.line.left.discussions.length > 0) ||

app/assets/javascripts/diffs/store/actions.js

@@ -49,6 +49,7 @@ export const assignDiscussionsToDiff = ({ state }, allLineDiscussions) => {
           }
         }
 
+        if (selectedFile.highlightedDiffLines) {
           const targetInlineLine = selectedFile.highlightedDiffLines.find(
             line => line.lineCode === discussions[0].line_code,
           );
@@ -58,6 +59,7 @@ export const assignDiscussionsToDiff = ({ state }, allLineDiscussions) => {
           }
         }
       }
+    }
   });
 };