added better logging when 'hack attempt is encountered', and fixed a …

[maltfield]

…logic bug that resulted in a false-positive of the "hack attempt" exit when a phplist subscribe page had 0 lists selected. For more info, see:

• https://discuss.phplist.org/t/purpose-of-hack-attempt-exit-in-subscribelib2-php/4578/

[bramley]

The case that needs to be handled is when $GLOBALS['pagedata']['lists'] is an empty string, because explode() on an empty string gives an unwanted empty array entry.

I think that it is quite ok to assume that $GLOBALS['pagedata']['lists'] is correctly formatted so there won't otherwise be any empty entries.

[samtuke]

@xh3n1 Did you already review this?

[samtuke]

@suelaP Seems like this is still in need of review and implementation of @bramley 's suggestions