some asserts in disk_io_thread. fix issue in torrent::initialize

src/block_cache.cpp

@@ -332,6 +332,9 @@ void block_cache::cache_hit(cached_piece_entry* p, void* requester, bool volatil
 // this can be pretty expensive
 //	INVARIANT_CHECK;
 
+	TORRENT_ASSERT(p);
+	TORRENT_ASSERT(p->in_use);
+
 	// move the piece into this queue. Whenever we have a cahe
 	// hit, we move the piece into the lru2 queue (i.e. the most
 	// frequently used piece). However, we only do that if the

src/disk_io_thread.cpp

@@ -2307,6 +2307,7 @@ namespace libtorrent
 		cached_piece_entry* pe = m_disk_cache.find_piece(j);
 		if (pe)
 		{
+			TORRENT_ASSERT(pe->in_use);
 #if TORRENT_USE_ASSERTS
 			pe->piece_log.push_back(piece_log_t(j->action));
 #endif

src/torrent.cpp

@@ -1741,11 +1741,13 @@ namespace libtorrent
 			m_connections_initialized = true;
 			// all peer connections have to initialize themselves now that the metadata
 			// is available
-			for (torrent::peer_iterator i = m_connections.begin();
-				i != m_connections.end();)
+			// copy the peer list since peers may disconnect and invalidate
+			// m_connections as we initialize them
+			std::vector<peer_connection*> peers = m_connections;
+			for (torrent::peer_iterator i = peers.begin();
+				i != peers.end(); ++i)
 			{
 				peer_connection* pc = *i;
-				++i;
 				if (pc->is_disconnecting()) continue;
 				pc->on_metadata_impl();
 				if (pc->is_disconnecting()) continue;