Serial Print makes code work. Why?

Projects Programming
7

The array holds constant cString so that definition should be

const char *titleStr[row * col] = {"4", "6", "8", "9", "12", "16", "Load", "1", nullptr, nullptr, nullptr, nullptr};`

Or

const char *titleStr[row * col] = {"4", "6", "8", "9", "12", "16", "Load", "1", "x", "xx", "xxx", "xxxx"};

If the library you are using does not deal well with null pointers. It would be necessary to understand what the library does with the information since the titles pointers are technically temporary (scope of the array is not global)