Codechange: Use null pointer literal instead of the NULL macro

src/strgen/strgen.h

@@ -73,7 +73,7 @@ struct StringReader {
 	 * Read a single line from the source of strings.
 	 * @param buffer The buffer to read the data in to.
 	 * @param last   The last element in the buffer.
-	 * @return The buffer, or NULL if at the end of the file.
+	 * @return The buffer, or nullptr if at the end of the file.
 	 */
 	virtual char *ReadLine(char *buffer, const char *last) = 0;