Index: trunk/ppStack/src/ppStack.c
===================================================================
--- trunk/ppStack/src/ppStack.c	(revision 27075)
+++ trunk/ppStack/src/ppStack.c	(revision 27076)
@@ -100,10 +100,12 @@
 
         // Ensure everything closes
-        ppStackFileActivation(config, PPSTACK_FILES_PREPARE, true);
-        ppStackFileActivation(config, PPSTACK_FILES_CONVOLVE, true);
-        ppStackFileActivation(config, PPSTACK_FILES_COMBINE, true);
-        ppStackFileActivation(config, PPSTACK_FILES_PHOT, true);
-        if (!ppStackFilesIterateUp(config)) {
-            psErrorStackPrint(stderr, "Unable to close files.");
+        if (config) {
+            ppStackFileActivation(config, PPSTACK_FILES_PREPARE, true);
+            ppStackFileActivation(config, PPSTACK_FILES_CONVOLVE, true);
+            ppStackFileActivation(config, PPSTACK_FILES_COMBINE, true);
+            ppStackFileActivation(config, PPSTACK_FILES_PHOT, true);
+            if (!ppStackFilesIterateUp(config)) {
+                psErrorStackPrint(stderr, "Unable to close files.");
+            }
         }