Index: /trunk/ppStack/src/ppStackLoop.c
===================================================================
--- /trunk/ppStack/src/ppStackLoop.c	(revision 17635)
+++ /trunk/ppStack/src/ppStackLoop.c	(revision 17636)
@@ -583,5 +583,7 @@
             for (int i = 0; i < num && more; i++) {
                 pmReadout *readout = readouts->data[i];
-                assert(readout);
+                if (!readout) {
+                    continue;
+                }
                 more &= pmReadoutMore(readout, imageFits->data[i], 0, numScans);
                 more &= pmReadoutMoreMask(readout, maskFits->data[i], 0, numScans);
@@ -593,4 +595,7 @@
         for (int i = 0; i < readouts->n; i++) {
             pmReadout *ro = readouts->data[i]; // Readout of interest
+            if (!ro) {
+                continue;
+            }
             pmReadoutFreeData(ro);
         }