Revert "Revert "newer standards prefer nullptr over NULL - this is most of them but there are others too""

This reverts commit 8e2160f33e.

engine/client/application/Miff/src/linux/OutputFileHandler.cpp

@@ -20,7 +20,7 @@
 OutputFileHandler::OutputFileHandler(const char *filename)
 {
 	outputIFF = new Iff(MAXIFFDATASIZE);
-	outFilename = NULL;
+	outFilename = nullptr;
 
 	setCurrentFilename(filename);
 }
@@ -45,7 +45,7 @@ OutputFileHandler::~OutputFileHandler(void)
 		delete [] outFilename;
 	}
 
-	outputIFF = NULL;
+	outputIFF = nullptr;
 }