make sure that unreferenced compounds are not mistaken as validated

FIX #216

ippisite/ippidb/models.py

@@ -895,6 +895,11 @@ class Compound(AutoFillableModel):
         return self.drugbankcompoundtanimoto_set.order_by("-tanimoto")
 
     def is_validated(self):
+        # if compound is not linked to any CompoundAction this is
+        # because it was dereferenced because of duplication by
+        # `replace_compound_references`
+        if self.compoundaction_set.count()==0:
+            return False
         for ca in self.compoundaction_set.all():
             if ca.ppi.contribution_set.filter(validated=False).exists():
                 return False