The ChartFragment gets its shinobiChart during ChartFragment.onCreate, so in your code it's still null at this time - all you've done so far is to instantiate it.
Presumably you're planning to do some chart setup using the ShinobiChart reference, so I'd suggest subclassing ChartFragment, and moving your setup code into its onCreate method (be sure to call super.onCreate(savedInstanceState);).
There's an example of this pattern in the CustomDataAdapter sample.