parseURI null check and error handling implemented (#710)

* parseURI null check and error handling implemented

* Cleaned and updated the changes according to restenb suggestion

Author: khanrn

src/cosim/osp_config_parser.cpp

@@ -614,10 +614,18 @@ struct extended_model_description
         const auto xerces_cleanup = final_action([]() {
             xercesc::XMLPlatformUtils::Terminate();
         });
+
         const auto domImpl = xercesc::DOMImplementationRegistry::getDOMImplementation(tc("LS").get());
         const auto parser = static_cast<xercesc::DOMImplementationLS*>(domImpl)->createLSParser(xercesc::DOMImplementationLS::MODE_SYNCHRONOUS, tc("http://www.w3.org/2001/XMLSchema").get());
+
         const auto doc = parser->parseURI(ospModelDescription.string().c_str());
-        // TODO: Check return value for null
+
+        if (doc == nullptr) {
+            std::ostringstream oss;
+            oss << "Validation of " << ospModelDescription.string() << " failed.";
+            BOOST_LOG_SEV(log::logger(), log::error) << oss.str();
+            throw std::runtime_error(oss.str());
+        }
 
         const auto rootElement = doc->getDocumentElement();