don't decrement due counts when spacing

This works fine if the user is showing all cards, but if they have limited
reviews to certain categories, it can result in the counts going negative
because we decremented for cards which weren't actually due. Determining if a
card was actually due or not is an expensive operation, so instead we leave
the counts alone and make sure reviews will finish early if the new/rev counts
are non-zero but the queue is empty.

anki/deck.py

@@ -673,7 +673,9 @@ limit %s""" % (self.cramOrder, self.queueLimit)))
             return self.revQueue[-1][0]
         # new cards left?
         if self.newCountToday:
-            return self.getNewCard()
+            id = self.getNewCard()
+            if id:
+                return id
         if check:
             # check for expired cards, or new day rollover
             self.updateCutoff()
@@ -711,12 +713,25 @@ limit %s""" % (self.cramOrder, self.queueLimit)))
             return False
 
     def getNewCard(self):
-        if (not self.newQueue or
-            self.spacedCards and
+        src = None
+        if (self.spacedCards and
             self.spacedCards[0][0] < time.time()):
+            # spaced card has expired
+            src = 0
+        elif self.newQueue:
+            # card left in new queue
+            src = 1
+        elif self.spacedCards:
+            # card left in spaced queue
+            src = 0
+        else:
+            # only cards spaced to another day left
+            return
+        if src == 0:
             cards = self.spacedCards[0][1]
             self.newFromCache = True
             return cards[0]
+        else:
             self.newFromCache = False
             return self.newQueue[-1][0]
 
@@ -870,20 +885,7 @@ where id in """
         self.setUndoEnd(undoName)
 
     def _spaceCards(self, card):
-        # update new counts
         new = time.time() + self.newSpacing
-        if new > self.dueCutoff:
-            self.newCount -= self.s.scalar("""
-select count() from cards
-where factId = :fid and id != :cid
-and combinedDue < :cut and type = 2
-""", cid=card.id, fid=card.factId, cut=self.dueCutoff)
-        # update due counts
-        self.revCount -= self.s.scalar("""
-select count() from cards
-where factId = :fid and id != :cid
-and combinedDue < :cut and type = 1
-""", cid=card.id, fid=card.factId, cut=self.dueCutoff)
         # space cards
         self.s.statement("""
 update cards set