replace NULL by nullptr on loadFile.

code/AMF/AMFImporter.cpp

@@ -407,7 +407,9 @@ void AMFImporter::ParseFile(const std::string& pFile, IOSystem* pIOHandler)
     std::unique_ptr<IOStream> file(pIOHandler->Open(pFile, "rb"));
 
 	// Check whether we can read from the file
-	if(file.get() == NULL) throw DeadlyImportError("Failed to open AMF file " + pFile + ".");
+    if (file.get() == nullptr) {
+        throw DeadlyImportError("Failed to open AMF file " + pFile + ".");
+    }
 
 	// generate a XML reader for it
 	std::unique_ptr<CIrrXML_IOStreamReader> mIOWrapper(new CIrrXML_IOStreamReader(file.get()));