Ensure that a premature call will not overwrite unrelated memory

driver/others/blas_server_win32.c

@@ -568,7 +568,7 @@ void goto_set_num_threads(int num_threads)
 			blas_server_avail = 1;
 		}
 
-		for(i = blas_num_threads - 1; i < num_threads - 1; i++){
+		for(i = (blas_num_threads > 0) ? blas_num_threads - 1 : 0; i < num_threads - 1; i++){
 
 			blas_threads[i] = CreateThread(NULL, 0,
 				     blas_thread_server, (void *)i,