Open-event-droidgen: App crashes on refreshing if no API link was provided

[the-dagger]

If the app was created from zip file, the app crashes when any of the fragment is refreshed.
We need to display a dialogue instead when this happen.

[mananwason]

@the-dagger You just need to provide an empty string from the server as the api link. You could also add a parameter to config.json that specifies if api link is not given and we can use Sharedpreference on the app to handle refresh

[mananwason]

Also in the case of empty string I have handled it with an error display in the app.