authorcolor storage optimization, add undefined checks before access, code styling

www/common/sframe-common-codemirror.js

@@ -423,7 +423,7 @@ define([
             var remoteDoc = newContent.content;
             // setValueAndCursor triggers onLocal, even if we don't make any change to the content
             // and it may revert other changes (metadata)
-            if (oldDoc === remoteDoc && authormarksUpdate == authormarksLocal) { return; }
+            if (oldDoc === remoteDoc && (authormarksUpdate === undefined || authormarksLocal === undefined || JSON.stringify(authormarksUpdate) === JSON.stringify(authormarksLocal))) { return; }
             exp.setValueAndCursor(oldDoc, remoteDoc);
         };