fix #8109

default behavior is conservative: if the body of a recursive function contains uninterpreted variables they are not rewritten.
Model evaluation will bind values to uninterpreted variables so the filter should not apply here.

src/ast/rewriter/th_rewriter.cpp

@@ -108,6 +108,7 @@ struct th_rewriter_cfg : public default_rewriter_cfg {
         m_ar_rw.updt_params(p);
         m_f_rw.updt_params(p);
         m_seq_rw.updt_params(p);
+        m_rec_rw.updt_params(p);
         updt_local_params(p);
     }