Don't hardcode colspan in WP_List_Table when there are no items

[garyc40]

Currently in WP_List_Table::display_rows_or_placeholder(), when there's no item, colspan = "2" is applied to the no-item cell despite the number of visible columns.

don't hardcode colspan

This something we need to address in 3.1? Sounds like it, and I think I've seen evidence of this in the UI with odd wrapping.

Looks good.

This doesn't take into account hidden columns.

Also, when you do take into account hidden columns with a - count( $hidden ), I get one more, as my array is this: array( 0 => 'response', 1 => '' ). Not a clue why I have the empty value, but an array_filter() can remove it if it isn't just me.

Seeing the same thing on other screens. Going to go with array_filter().

(In [17339]) Properly account for columns shown in the list table display_rows_or_placeholder methods. props garyc40, fixes #16279.

Use get_column_count()

There's a dedicated method for that: get_column_count(). See 16279.diff​.

(In [17342]) Use get_column_count() instead of manual logic. props scribu, fixes #16279.