I get the following error with a table with only one column:

Warning: array_fill() [<a href='function.array-fill'>function.array-fill</a>]: Number of elements must be positive in lib/tablelib.php on line 1043

It seems to be caused by the "-1" after the count. There is no error without the "-1" or with two columns.

The change was introduced in MDL-36011.