fix invariant check

include/libtorrent/piece_picker.hpp

@@ -215,6 +215,15 @@ namespace libtorrent
 			return m_piece_map[index].index == piece_pos::we_have_index;
 		}
 
+		bool is_downloading(int index) const
+		{
+			TORRENT_ASSERT(index >= 0);
+			TORRENT_ASSERT(index < int(m_piece_map.size()));
+
+			piece_pos const& p = m_piece_map[index];
+			return p.downloading;
+		}
+
 		// sets the priority of a piece.
 		// returns true if the priority was changed from 0 to non-0
 		// or vice versa

src/torrent.cpp

@@ -6485,7 +6485,12 @@ namespace libtorrent
 				piece_block b = i->first;
 				int count = i->second;
 				int picker_count = m_picker->num_peers(b);
-				if (!m_picker->is_downloaded(b))
+				// if we're no longer downloading the piece
+				// (for instance, it may be fully downloaded and waiting
+				// for the hash check to return), the piece picker always
+				// returns 0 requests, regardless of how many peers may still
+				// have the block in their queue
+				if (!m_picker->is_downloaded(b) && m_picker->is_downloading(b.piece_index))
 					TORRENT_ASSERT(picker_count == count);
 			}
 			TORRENT_ASSERT(num_have() >= m_picker->num_have_filtered());