use dynamic cast instead of c-style cast when casting from base type to derived class

src/pair_hybrid.cpp

@@ -115,7 +115,7 @@ void PairHybrid::compute(int eflag, int vflag)
   Respa *respa = nullptr;
   respaflag = 0;
   if (utils::strmatch(update->integrate_style,"^respa")) {
-    respa = (Respa *) update->integrate;
+    respa = dynamic_cast<Respa *>( update->integrate);
     if (respa->nhybrid_styles > 0) respaflag = 1;
   }