Fixes issue where ecK was used as numberOfSlots.

codex/manifest/manifest.nim

@@ -98,6 +98,12 @@ proc verificationRoot*(self: Manifest): Cid =
 proc slotRoots*(self: Manifest): seq[Cid] =
   self.slotRoots
 
+proc numberOfSlots*(self: Manifest): int =
+  if not self.protected:
+    0
+  else:
+    self.ecK + self.ecM
+
 ############################################################
 # Operations on block list
 ############################################################

codex/slotbuilder/slotbuilder.nim

@@ -51,7 +51,7 @@ proc selectSlotBlocks*(self: SlotBuilder, datasetSlotIndex: int): Future[?!seq[C
   let
     datasetTreeCid = self.manifest.treeCid
     blockCount = self.manifest.blocksCount
-    numberOfSlots = self.manifest.ecK
+    numberOfSlots = self.manifest.numberOfSlots
     strategy = SteppedIndexingStrategy.new(0, blockCount - 1, numberOfSlots)
 
   for datasetBlockIndex in strategy.getIndicies(datasetSlotIndex):