Exception in v2.1.5 demo app in compiled mode

`shakaDemo.player_.defaultConfig_` is not accessible in compiled mode and causes an exception in the demo app.  I didn't catch it before I tagged v2.1.5.

This only affects the demo and no other applications.  The bug is in the demo itself.  This should be fixed before v2.2.0 and cherry-picked to v2.1.6.