Index: /trunk/ppStack/src/ppStackReadout.c
===================================================================
--- /trunk/ppStack/src/ppStackReadout.c	(revision 23345)
+++ /trunk/ppStack/src/ppStackReadout.c	(revision 23346)
@@ -232,5 +232,6 @@
         }
 
-        pmStackData *data = pmStackDataAlloc(ro, weightings->data.F32[i], addVariance->data.F32[i]);
+        pmStackData *data = pmStackDataAlloc(ro, weightings->data.F32[i],
+                                             addVariance ? addVariance->data.F32[i] : NAN);
         data->reject = psMemIncrRefCounter(rejected->data[i]);
         stack->data[i] = data;