fix DropLocalExeScopes (#17829)

test=develop

paddle/fluid/framework/details/scope_buffered_ssa_graph_executor.cc

@@ -65,12 +65,15 @@ void ScopeBufferedSSAGraphExecutor::DropLocalExeScopes() {
   for (auto p : places_) {
     platform::DeviceContextPool::Instance().Get(p)->Wait();
   }
+
   for (auto &scope : local_scopes_) {
-    auto &local_scope =
-        *scope->Var(details::kLocalExecScopeName)->GetMutable<Scope *>();
+    auto *local_scope_var = scope->FindLocalVar(details::kLocalExecScopeName);
+    if (local_scope_var != nullptr) {
+      auto &local_scope = *local_scope_var->GetMutable<Scope *>();
       scope->DeleteScope(local_scope);
       VLOG(3) << "Drop local execution scope: " << local_scope;
     }
+  }
 }
 
 void ScopeBufferedSSAGraphExecutor::PrepareLocalExeScopes() {