Ignore empty values for revision.

Fixes #420

Author: SISheogorath

lib/models/revision.js

@@ -237,8 +237,8 @@ module.exports = function (sequelize, DataTypes) {
             // if no revision available
             Revision.create({
               noteId: note.id,
-              lastContent: note.content,
-              length: note.content.length,
+              lastContent: note.content ? note.content : '',
+              length: note.content ? note.content.length : 0,
               authorship: note.authorship
             }).then(function (revision) {
               Revision.finishSaveNoteRevision(note, revision, callback)