Allowed to construct a dbus::BusConnection object with NULL g_connection

chromeos/dbus/dbus.h

 // Copyright (c) 2009 The Chromium OS Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROMEOS_DBUS_H_
 #define CHROMEOS_DBUS_H_
 
 #include <dbus/dbus-glib.h>
 #include <glib-object.h>
 
@@ skipping 16 matching lines @@
 // bus.
 //
 // \models Copyable, Assignable
 // \related GetSystemBusConnection()
 
 class BusConnection {
  public:
   typedef ::DBusGConnection* value_type;
 
   BusConnection(const BusConnection& x)
-      : object_(dbus_g_connection_ref(x.object_)) {
+      : object_(x.object_) {
+    if (object_)
+      ::dbus_g_connection_ref(object_);
   }
 
   ~BusConnection() {
-    ::dbus_g_connection_unref(object_);
+    if (object_)
+      ::dbus_g_connection_unref(object_);
   }
 
   BusConnection& operator=(BusConnection x) {
     swap(*this, x);
     return *this;
   }
 
   const value_type& g_connection() const {
     DCHECK(object_) << "referencing an empty connection";
     return object_;
   }
 
+  operator bool() const {
+    return object_;
+  }
+
+  bool HasConnection() const {
+    return object_;
+  }
+
  private:
   friend void swap(BusConnection& x, BusConnection& y);
 
   friend class Proxy;
   friend BusConnection GetSystemBusConnection();
   friend BusConnection GetPrivateBusConnection(const char* address);
 
   // Constructor takes ownership
   explicit BusConnection(::DBusGConnection* x)
       : object_(x) {
-    DCHECK(object_) << "Constructing BusConnection with NULL object.";
   }
 
   value_type object_;
 };
 
 inline void swap(BusConnection& x, BusConnection& y) {
   std::swap(x.object_, y.object_);
 }
 
 // \brief Proxy manages the ref-count for a ::DBusGProxy*.
@@ skipping 275 matching lines @@
 BusConnection GetSystemBusConnection();
 
 // \brief Returns a private connection to a bus at |address|.
 
 BusConnection GetPrivateBusConnection(const char* address);
 
 }  // namespace dbus
 }  // namespace chromeos
 
 #endif  // CHROMEOS_DBUS_H_