fix #7554

mbp_qel  uses two iterations of saturation.
The first iteration uses only congruences, not the model.
The second iteration uses the model.
Terms are marked as "seen" during either iteration and will not be reprocessed if they are "seen".
All select terms get marked as "seen" to avoid reproducing Ackerman axioms.
But this conflicts with expanding select-store axioms during
the phase of saturation where use_model is allowed.

Author: NikolajBjorner

src/qe/mbp/mbp_arrays_tg.cpp

@@ -401,9 +401,13 @@ struct mbp_array_tg::impl {
             if (m_array_util.is_select(term) &&
                 has_var(to_app(term)->get_arg(0))) {
                 rdTerms.push_back(to_app(term));
-                if (is_seen(term)) continue;
+                if (is_seen(term)) 
+                    continue;
                 add_rdVar(term);
-                mark_seen(term);
+                // select-store axioms are only introduced during m_use_mdl
+                // so don't mark select-store terms if m_use_mdl is false
+                if (m_use_mdl || !m_array_util.is_store(to_app(term)->get_arg(0)))
+                    mark_seen(term);
             }
         }
         if (!m_use_mdl)