Index: trunk/psModules/src/objects/pmSource.c
===================================================================
--- trunk/psModules/src/objects/pmSource.c	(revision 29546)
+++ trunk/psModules/src/objects/pmSource.c	(revision 29935)
@@ -189,6 +189,6 @@
     // pixels.  Modifying these pixels (ie, subtracting the model) will affect the pixels seen
     // by all copies.
-    source->pixels   = psImageCopyView(NULL, in->pixels);
-    source->variance   = psImageCopyView(NULL, in->variance);
+    source->pixels   = in->pixels   ? psImageCopyView(NULL, in->pixels)   : NULL;
+    source->variance = in->variance ? psImageCopyView(NULL, in->variance) : NULL;
     source->maskView = in->maskView ? psImageCopyView(NULL, in->maskView) : NULL;