remove_help_tab() not working as expected

[tfnab]

remove_help_tab takes $id as a parameter. this is either confusing or wrong. the method does the following:

unset( $this->_help_tabs[ $id ] );

but since add_help_tab simply does this:

$this->_help_tabs[] = $args;

you have to call remove_help_tab with numerical values such as 0, 1, 2 etc. but not the 'this-id' passed in e.g.

add_help_tab(array('id'=>'this-id',...

in addition if you remove the zero element, initially there is no active tab on the help tab.

fix attached. this makes the following line remove the previously created tab:

remove_help_tab('this-id');

I noticed this in #19974 and fixed it in [19944].