Index: trunk/ppStack/src/ppStackReadout.c
===================================================================
--- trunk/ppStack/src/ppStackReadout.c	(revision 15303)
+++ trunk/ppStack/src/ppStackReadout.c	(revision 15397)
@@ -260,5 +260,5 @@
 #endif
 
-    for (int i = 0; i < num; i++) {
+    for (int i = 0; i < stack->n; i++) {
         pmStackData *data = stack->data[i]; // Data for this image
         pmReadout *readout = data->readout; // Readout for this image
@@ -299,6 +299,9 @@
 
 #ifdef REJECTION_FILES
-    for (int i = 0; i < num; i++) {
+    for (int i = 0; i < stack->n; i++) {
         pmStackData *data = stack->data[i]; // Data for this image
+        if (!data) {
+            continue;
+        }
         psImage *rejected = psPixelsToMask(NULL, data->pixels,
                                            psRegionSet(0, data->readout->image->numCols,