fix for issue 642. noticed thier is a whole slew of bugs in story mode that didn't exist before. this mode has been neglected and we should consider taking some time to bring it back up to standard.

i'll open some tickets for it later.

projects/mtg/src/ActionStack.cpp

@@ -619,6 +619,8 @@ Spell * ActionStack::addSpell(MTGCardInstance * _source, TargetChooser * tc, Man
 
 Interruptible * ActionStack::getAt(int id)
 {
+    if (!mObjects.size())//nothing to get.
+        return NULL;
     if (id < 0)
         id = mCount + id;
     if (id > mCount - 1)