filetransfer: assert maxQueueSize > 0

A queue size of 0 will cause hanging in the file transfer process.

Author: cole-h

src/libstore/filetransfer.cc

@@ -780,6 +780,9 @@ struct curlFileTransfer : public FileTransfer
 
     void workerThreadMain()
     {
+        /* NOTE(cole-h): the maxQueueSize needs to be >0 or else things will hang */
+        assert(maxQueueSize > 0);
+
 /* Cause this thread to be notified on SIGINT. */
 #ifndef _WIN32 // TODO need graceful async exit support on Windows?
         auto callback = createInterruptCallback([&]() { stopWorkerThread(); });