problem with dead rule elimination and "Rules with overlapping objects" test

```
[ Present Present ] -> [ Present Present TempCheck ]
+[ ] -> [ ]
```
and

```
[ ] -> [ ]
+[ Present Present ] -> [ Present Present TempCheck ]
+[ ] -> [ ]
```

trigger elimination message, but not

```
[ ] -> [ ]
+[ Present Present ] -> [ Present Present TempCheck ]
```

(related to #808 )

