Index: trunk/pswarp/src/pswarpTransformReadout.c
===================================================================
--- trunk/pswarp/src/pswarpTransformReadout.c	(revision 28547)
+++ trunk/pswarp/src/pswarpTransformReadout.c	(revision 28548)
@@ -200,5 +200,7 @@
             return false;
         }
-
+    }
+
+    if (goodPixels > 0) {
         // Data is only written out if there are good pixels
         output->data_exists = true;