apps crashes when navigating in it

[Donatas Baliuka]

I downloaded an apps with a fixed synchronization error from http://mobile.openerp.co.in/_downloads/openerp-mobile-crm.zip
I adapted the leads for our database. The apps crashes in these cases:
1) When I choose to display the leads list second time it crashes on this line in Lead.java:
OEDataRow row = (OEDataRow) mLeadItems.get(position);
Logcat shows that position is 0 and size of mLeadItems is 0.
I added a check: if (mLeadsItems.size>position)
This allows to display leads list more times.

After this I noticed more cases when the apps crashed:
2) The apps crashes on navigating with back button( the logcat writes that "fragment is already set");

3)The apps crashes when the orientation of a device is changed from landscape to portrait or vice versa.

[Donatas Baliuka (donatas-baliuka-0)]

I analyzed crashes of type 3 and noticed that some classes derived from BaseFragment(eg. AboutFragment)
have code:
public void onDestroy() {
  super.onDestroy();
  scope.main().getActionBar().setDisplayHomeAsUpEnabled(true);
  scope.main().getActionBar().setHomeButtonEnabled(true);
 }
and some have code:
public void onStop() {
 {
  super.onStop();
  scope.main().getActionBar().setDisplayHomeAsUpEnabled(true);
  scope.main().getActionBar().setHomeButtonEnabled(true);
 }

Crashes sometimes happen in the classes with onDestroy() method( null pointer exception).
I have a question: When a class must have code in the method onDestroy() and when in the method onStop()?