I Can't Solve NoReverseMatch at /events/ Error - django

Question

I got this error when I add event with status false. There is no problem at status true:
NoReverseMatch at /events/
Reverse for 'event-detail' with arguments '('',)' not found. 1 pattern(s) tried: ['events/(?P<url_sistem>[^/]+)/$']
I couldn't see the cause of the error
It's my views.py file:
from django.shortcuts import render, get_object_or_404
from .models import Event
def event_list(request):
events_f = Event.objects.filter(status=False)
events_t = Event.objects.filter(status=True)
return render(request, 'etkinlik/event_list.html', {'events_f':events_f , 'events_t':events_t})
def event_detail(request, url_sistem):
event = get_object_or_404(Event, url_sistem=url_sistem)
return render(request, 'etkinlik/event_detail.html',{'event':event})
This is urls.py:
urlpatterns = [
path('', views.event_list, name='event_list'),
path('<str:url_sistem>/', views.event_detail, name='event-detail')
]
And this template file:
{% extends 'base.html' %}
{%block title%}Events | {%endblock%}
{% block content %}
<div class="container mt-4">
<div class="jumbotron">
<h4 class="display-4">Öne Çıkarılan Etkinlik</h4>
<p class="lead mb-5">Bu etkinlik şuandaki en önemli ve popüler etkinliktir. Katılabilen herkesin katılmasını isteriz</p>
{% if not events_t %}
<h2>Şu anda öne çıkarılan yok</h2>
{% else %}
{% for event_t in events_t %}
<a href="{% url 'event-detail' event_t.url_sistem %}" style="color:black;">
<div class="card mb-3" style="max-width:700px;">
<div class="row no-gutters">
<div class="col-md-4">
<img src="/media/{{ event_t.img_event }}" class="card-img" alt="etkinlik_foto">
</div>
<div class="col-md-8">
<div class="card-body">
<h5 class="card-title">{{event_t.title}}</h5>
<p class="card-text">{{event_t.exp}}</p>
<p class="card-text"><small class="text-muted">Etkinlik Tarihi: {{event_t.event_date}}</small></p>
</div>
</div>
</div>
</div>
</a>
{% endfor %}
{% endif %}
</div>
{% for event_f in events_f %}
<a href="{% url 'event-detail' event_t.url_sistem %}" style="color:black;">
<div class="card mb-3" style="max-width:700px;">
<div class="row no-gutters">
<div class="col-md-4">
<img src="/media/{{ event_f.img_event }}" class="card-img" alt="etkinlik_foto">
</div>
<div class="col-md-8">
<div class="card-body">
<h5 class="card-title">{{event_f.title}}</h5>
<p class="card-text">{{event_f.exp}}</p>
<p class="card-text"><small class="text-muted">Etkinlik Tarihi: {{event_f.event_date}}</small></p>
</div>
</div>
</div>
</div>
</a>
{% endfor %}
</div>
{% endblock %}
Thanks in advance

Answer 1

<a href="{% url 'event-detail' event_t.url_sistem %}" style="color:black;">
Here in the url you need to replace event_t.url_sistem with event_f.url_sistem