Make sequences record whether they have been visited or not (done somewhat…

Make sequences record whether they have been visited or not (done somewhat implicitly now, would be nice to be more explicit)

common/lib/xmodule/xmodule/seq_module.py

@@ -37,7 +37,7 @@ class SequenceModule(XModule):
 
     # NOTE: Position is 1-indexed.  This is silly, but there are now student
     # positions saved on prod, so it's not easy to fix.
-    position = Int(help="Last tab viewed in this sequence", default=1, scope=Scope.student_state)
+    position = Int(help="Last tab viewed in this sequence", scope=Scope.student_state)
 
     def __init__(self, *args, **kwargs):
         XModule.__init__(self, *args, **kwargs)
@@ -46,6 +46,13 @@ class SequenceModule(XModule):
         if self.system.get('position'):
             self.position = int(self.system.get('position'))
 
+        # Default to the first child
+        # Don't set 1 as the default in the property definition, because
+        # there is code that looks for the existance of the position value
+        # to determine if the student has visited the sequence before or not
+        if self.position is None:
+            self.position = 1
+
         self.rendered = False
 
     def get_instance_state(self):