message: If we can't print the msg, at least print its code
diff: @@ -19,7 +19,7 @@ std::string gl::last_error()
  return std::string(reinterpret_cast<char const*>(glewGetErrorString(err)));
  #endif
  }
  - return "";
  + return std::to_string(err);
  }
  void gl::alloc_texture(pixel_format_info info, GLsizei w, GLsizei h)
  