Index: /branches/eam_branches/ipp-pstamp-20260421/PS-IPP-PStamp/lib/PS/IPP/PStamp/Job.pm
===================================================================
--- /branches/eam_branches/ipp-pstamp-20260421/PS-IPP-PStamp/lib/PS/IPP/PStamp/Job.pm	(revision 43085)
+++ /branches/eam_branches/ipp-pstamp-20260421/PS-IPP-PStamp/lib/PS/IPP/PStamp/Job.pm	(revision 43086)
@@ -1151,7 +1151,9 @@
         
     } else {
-        # this should have been checked elsewhere
-        die "unexpected image type $stage" if ($stage ne "warp") 
-                                              and ($stage ne "stack") and ($stage ne "diff");
+        # this should have been checked elsewhere (PHP code or calling program)
+        die "unexpected image type $stage" if ($stage ne "warp") and ($stage ne "stack") and ($stage ne "diff");
+
+        # this should have also been checked elsewhere (PHP code)
+	die "missing TESS_ID for request by coordinates of warp, stack, or diff" unless (@tess_ids);
 
         foreach my $tess_id (@tess_ids) {