Issue #81: TypeError undefined not an object
Issue #81: TypeError undefined not an object

Kind of a regression bug. Systems that lacks indexedDB should get a
promise rejection on db.open() not a TypeError thrown at them.

jimmywarting/Dexie.js,jimmywarting/Dexie.js,dfahlander/Dexie.js,jacobmarshall/ng-dexie,dfahlander/Dexie.js,chrahunt/Dexie.js,dfahlander/Dexie.js,jimmywarting/Dexie.js,cesarmarinhorj/Dexie.js,cesarmarinhorj/Dexie.js,jacobmarshall/ng-dexie,YuriSolovyov/Dexie.js,dfahlander/Dexie.js,YuriSolovyov/Dexie.js,jimmywarting/Dexie.js,chrahunt/Dexie.js,chrahunt/Dexie.js,chrahunt/Dexie.js