[lldb][lldb-vscode] Fix nullptr dereference when JSON is not an object

[wallace]

thanks

lldb/tools/lldb-vscode/VSCode.cpp

 //===-- VSCode.cpp ----------------------------------------------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
if (log) {
       llvm::raw_string_ostream strm(error_str);
       strm << error;
       strm.flush();
       *log << "error: failed to parse JSON: " << error_str << std::endl
            << json << std::endl;
     }
     return PacketStatus::JSONMalformed;
   }
-  object = *json_value->getAsObject();
-  if (!json_value->getAsObject()) {
+  llvm::json::Object *object_ptr = json_value->getAsObject();
+  if (!object_ptr) {
     if (log)
       *log << "error: json packet isn't a object" << std::endl;
     return PacketStatus::JSONNotObject;
   }
+  object = *object_ptr;
   return PacketStatus::Success;
 }
 
 bool VSCode::HandleObject(const llvm::json::Object &object) {
   const auto packet_type = GetString(object, "type");
   if (packet_type == "request") {
     const auto command = GetString(object, "command");
     auto handler_pos = request_handlers.find(std::string(command));