[Plugin: Events Manager] Ticket Start End Date not cleared ?

I was noticing that my tickets did not show and users cannot register for an event while I did not set any date range for registration of events.
Dumping the ticket object variables I noticed this:

[0] => EM_Ticket Object
                (
                    [id] => 86
                    [event_id] => 258
                    [name] => Standard Ticket
                    [price] => 95.00
                    [start] => 2011-08-24 00:00:00
                    [end] => 2011-10-02 00:00:00

Start and end are set!! That was LONG time and I had cleared the entries. Now, what to do ? I will need to find the stuff in the DB and clear the date, I guess. As I have already people booked, I cannot re-edit the event as I loos the attendees…..

Here the EM script fails then and does not offer a Ticket List:

function is_available(){
		$timestamp = current_time('timestamp');
		$available_spaces = $this->get_available_spaces();//8
		$val = (empty($this->start) || $this->start_timestamp <= $timestamp);
function is_available(){
   $timestamp = current_time('timestamp');
   $available_spaces = $this->get_available_spaces();//8
   $val = (empty($this->start) || $this->start_timestamp <= $timestamp);
   $val2 = ($this->end_timestamp >= $timestamp || empty($this->end));
   $val3 = $this->get_event()->end > current_time('timestamp');

   echo "<br>Bol 1: ".(empty($this->start) || $this->start_timestamp <= $timestamp);
   echo "<br>Bol 2:'$this->end' ".(empty($this->end)   || $this->end_timestamp   >= $timestamp);
   echo "<br>Bol 3: ".($this->get_event()->end > current_time('timestamp'));

   if(   (empty($this->start) || $this->start_timestamp <= $timestamp)
      && (empty($this->end)   || $this->end_timestamp   >= $timestamp)
      && $this->get_event()->end > current_time('timestamp')
      ){
....the list

Hints and tips ?

https://www.ads-software.com/extend/plugins/events-manager/