clear tactic user propagate state on solver destructor

src/tactic/tactical.cpp

@@ -192,6 +192,10 @@ public:
         return m_t2->user_propagate_register(e);
     }
 
+    void user_propagate_clear() override {
+        m_t2->user_propagate_clear();
+    }
+
 };
 
 tactic * and_then(tactic * t1, tactic * t2) {

src/tactic/user_propagator_base.h

@@ -56,6 +56,9 @@ namespace user_propagator {
         virtual unsigned user_propagate_register(expr* e) { 
             throw default_exception("user-propagators are only supported on the SMT solver");
         }
+
+        virtual void user_propagate_clear() {
+        }
        
     };