Merge pull request #221 from mtconnect/monitor_file_change_device_issues

Author: wsobel

CMakeLists.txt

@@ -3,7 +3,7 @@ set(AGENT_VERSION_MAJOR 2)
 set(AGENT_VERSION_MINOR 0)
 set(AGENT_VERSION_PATCH 0)
 set(AGENT_VERSION_BUILD 12)
-set(AGENT_VERSION_RC "_RC20")
+set(AGENT_VERSION_RC "_RC21")
 
 # This minimum version is to support Visual Studio 2017 and C++ feature checking and FetchContent
 cmake_minimum_required(VERSION 3.16 FATAL_ERROR)

src/agent.cpp

@@ -389,8 +389,11 @@ namespace mtconnect {
         if (version)
           versionDeviceXml();
 
-        auto d = m_agentDevice->getDeviceDataItem("device_changed");
-        m_loopback->receive(d, *uuid);
+        if (m_agentDevice)
+        {
+          auto d = m_agentDevice->getDeviceDataItem("device_changed");
+          m_loopback->receive(d, *uuid);
+        }
 
         return true;
       }

src/device_model/data_item/data_item.cpp

@@ -250,9 +250,18 @@ namespace mtconnect {
     bool DataItem::operator<(const DataItem &another) const
     {
       auto component = m_component.lock();
+      if (component == nullptr)
+        return true;
+      auto dev = component->getDevice();
+      if (dev == nullptr)
+        return true;
+
       auto otherComponent = another.getComponent();
+      if (otherComponent == nullptr)
+        return false;
       auto otherDev = otherComponent->getDevice();
-      auto dev = component->getDevice();
+      if (otherDev == nullptr)
+        return false;
 
       if (dev->getId() < otherDev->getId())
         return true;