Check interupts even when download stalled

src/libstore/filetransfer.cc

@@ -828,15 +828,14 @@ void FileTransfer::download(FileTransferRequest && request, Sink & sink)
         {
             auto state(_state->lock());
 
-            while (state->data.empty()) {
-
             if (state->quit) {
                 if (state->exc) std::rethrow_exception(state->exc);
                 return;
             }
 
             state.wait(state->avail);
-            }
+
+            if (state->data.empty()) continue;
 
             chunk = std::move(state->data);