fixed issue with 0-sized torrents and verify_piece assert

src/peer_connection.cpp

@@ -3104,7 +3104,8 @@ namespace libtorrent
 				}
 			}
 
-			TORRENT_ASSERT(verify_piece(r));
+			// the verification will fail for coalesced blocks
+			TORRENT_ASSERT(verify_piece(r) || m_request_large_blocks);
 			
 #ifndef TORRENT_DISABLE_EXTENSIONS
 			bool handled = false;

src/torrent.cpp

@@ -817,6 +817,13 @@ namespace libtorrent
 			return;
 		}
 
+		if (m_torrent_file->num_pieces() == 0)
+		{
+			set_error(errors::torrent_invalid_length, "");
+			pause();
+			return;
+		}
+
 		// the shared_from_this() will create an intentional
 		// cycle of ownership, se the hpp file for description.
 		m_owning_storage = new piece_manager(shared_from_this(), m_torrent_file