flow improvements

include/client.hpp

@@ -5,6 +5,7 @@ int transfer_files(size_t index, AccountUid uid);
 bool isClientTransferDone();
 bool isClientTransferCancelled();
 bool isClientConnectionFailed();
+bool isClientProgressKnown();
 void cancelClientTransfer();
 double getClientProgress();
 std::string getClientStatusText();