Default Buffer::write_to_file statistic output pointers to nullptr

src/core/Buffer.h

@@ -156,7 +156,7 @@ public:
     Buffer();
     Buffer(const char * filename);
     Buffer(const uint8_t * data, size_t data_length);
-    bool write_to_file(const char * filename, size_t * n_lines, size_t * n_bytes);
+    bool write_to_file(const char * filename, size_t * n_lines = nullptr, size_t * n_bytes = nullptr);
 
     std::shared_ptr<Iterator> add_iterator()
     {