Fix "Cannot call method 'toLowerCase' of undefined" error

sequelize/lib/dao.js:139
ap(function(d) { return d.toLowerCase() }).indexOf(values[attrName].toLowerCas
                                                                    ^
TypeError: Cannot call method 'toLowerCase' of undefined

lib/dao.js

@@ -135,7 +135,7 @@ module.exports = (function() {
               , ciCollation     = !!self.daoFactory.options.collate && self.daoFactory.options.collate.match(/_ci$/i)
               , ciCollation     = !!self.daoFactory.options.collate && self.daoFactory.options.collate.match(/_ci$/i)
 
 
             // Unfortunately for MySQL CI collation we need to map/lowercase values again
             // Unfortunately for MySQL CI collation we need to map/lowercase values again
-            if (isEnum && isMySQL && ciCollation) {
+            if (isEnum && isMySQL && ciCollation && (attrName in values)) {
               var scopeIndex = (definition.values || []).map(function(d) { return d.toLowerCase() }).indexOf(values[attrName].toLowerCase())
               var scopeIndex = (definition.values || []).map(function(d) { return d.toLowerCase() }).indexOf(values[attrName].toLowerCase())
               valueOutOfScope = scopeIndex === -1
               valueOutOfScope = scopeIndex === -1