spamfilter_wblist - Entrys remain in DB after Customer Delete

short description

Entrys of spamfilter_wblist remain after client deletion. This happens if rid is 0 and also when the foreign key spamfilter_wblist.rid is = spamfilter_users.id is set.

correct behaviour

Deletion when User ist deleted

environment

Server OS: Debian Server OS version: Stretch ISPConfig version: 3.1.7 p1 you can use grep 'ISPC_APP_VERSION' /usr/local/ispconfig/server/lib/config.inc.php to get it from the command line

insert the output of `nginx -v` or `apachectl -v` here
Server version: Apache/2.4.25 (Debian)
Server built:   2017-09-19T18:58:57

insert the output of `php -v` here
PHP 7.0.19-1 (cli) (built: May 11 2017 14:04:47) ( NTS )

## proposed fix
optional, of course.  
if you want to post code snippets, please use

proposed fix

optional, of course.
if you want to post code snippets, please use

your code  

or attach a code file. Best is to create a merge request of course.

references

if you know of related bugs or feature requests, please reference them by using #<bugnumber>, e. g. #123 (closed)
if you have done a merge request already, please reference it by using !<mergenumber>, e. g. !12 (merged)
if you know of a forum post on howtoforge.com that deals with this topic, just add the link to the forum topic here

screenshots

optional, of course.
Add screenshots of the problem by clicking "Attach a file" on the bottom right.

log entries

apache / nginx error.log lines (if related)