Fix for a check that fails if no file can be selected

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

@@ -86,6 +86,7 @@ export default {
 
   [types.SET_LINE_DISCUSSIONS_FOR_FILE](state, { fileHash, discussions }) {
     const selectedFile = state.diffFiles.find(f => f.fileHash === fileHash);
+    if (selectedFile) {
       const firstDiscussion = discussions[0];
       const targetLine = selectedFile.parallelDiffLines.find(
         line =>
@@ -115,10 +116,12 @@ export default {
           });
         }
       }
+    }
   },
 
   [types.REMOVE_LINE_DISCUSSIONS_FOR_FILE](state, { fileHash, lineCode }) {
     const selectedFile = state.diffFiles.find(f => f.fileHash === fileHash);
+    if (selectedFile) {
       const targetLine = selectedFile.parallelDiffLines.find(
         line =>
           (line.left && line.left.lineCode === lineCode) ||
@@ -143,5 +146,6 @@ export default {
           });
         }
       }
+    }
   },
 };