Cannot read property 'ev' of null

‘Cannot read property ‘ev’ of null’ error. Sometimes while pressing pressing back button in ionic 2.

Cordova CLI: 6.4.0
Ionic Framework Version: 2.0.0-rc.5
Ionic CLI Version: 2.1.4
Ionic App Lib Version: 2.1.2
Ionic App Scripts Version: 1.0.0
OS: Distributor ID: Ubuntu Description: Ubuntu 15.10
Node Version: v7.4.0

Are you trying to capture and event when the back button is pressed?

No, of course not. It just happening. Since back button is ionic back end generated I can’t catch it (so far). Happy to hear suggestions…