Prevent Build from putting groups inside groups

[yanokwa]

A field-list group inside another field-list group crashes Collect. Build should not allow such forms to be built.

E/AndroidRuntime( 7503): java.lang.RuntimeException: Only questions are allowed in 'field-list'.  Bad node is: /data
E/AndroidRuntime( 7503):    at org.odk.collect.android.logic.FormController.getQuestionPrompts(FormController.java:848)
E/AndroidRuntime( 7503):    at org.odk.collect.android.logic.FormController.stepToNextScreenEvent(FormController.java:593)
E/AndroidRuntime( 7503):    at org.odk.collect.android.activities.FormEntryActivity.showNextView(FormEntryActivity.java:1174)
E/AndroidRuntime( 7503):    at org.odk.collect.android.activities.FormEntryActivity.onFling(FormEntryActivity.java:2467)
E/AndroidRuntime( 7503):    at android.view.GestureDetector.onTouchEvent(GestureDetector.java:600)    

[issa-tseng]

Erm, let's clarify this: generally groups inside of groups are just fine, right? It's just the field-list combo that breaks it? Or is it any group in a field-list group? What are the actual conditions?

[yanokwa]

Groups inside groups are fine. I think the rule is that you can only have individual questions inside a field-list group.