Slug returns Reverse for '' with arguments '('',)' not found. 1 pattern(s)

I am trying to make it so when I view a blog from any particular link on my website, the url displays I have got it working for my images and image title. But I cannot get it to work with blog titles.

It keeps returning the error:

Reverse for 'viewblog' with arguments '('',)' not found. 1 pattern(s) tried: ['view\-blog/(?P[-a-zA-Z0-9_]+)/\Z'].

class BlogPost(models.Model):
    blog_title = models.CharField(max_length=100, null=False, blank=False, default="")
    slug = models.SlugField()
    blog_article = RichTextUploadingField(null=True, blank=True, default="ici")
    blog_image = models.ImageField(null=True, blank=True, upload_to="images", default="default.png")
    blog_date = models.DateField(auto_now_add=True)
    blog_published = models.BooleanField(default=False)
    blog_featured = models.BooleanField(default=False)
    def save(self, *args, **kwargs):
        self.slug = self.slug or slugify(self.blog_title)
        super().save(*args, **kwargs)

    def __str__(self):
        return self.blog_title

def viewBlog(request, slug):
        blog = BlogPost.objects.get(slug=slug)
    except BlogPost.DoesNotExist:
        print("ViewBlog with this slug does not exist")
        blog = None
    return render(request, 'view-blog.html', {'blog': blog, 'slug': slug})

urlpatterns = [
    path('', views.galleryPage, name='gallery'),
    path('gallery/', views.galleryPage, name='gallery'),
    path('contact/', views.contactPage, name='contact'),
    path('blog/', views.blogPage, name='blog'),
    path('blogs/', views.blogsPage, name='blogs'),
    path('search-blogs/', views.searchBlogs, name='searchblogs'),
    path('view-image/<slug:slug>/', views.viewImage, name='viewimage'),
    path('view-blog/<slug:slug>/', views.viewBlog, name='viewblog'),
    path('thank-you/', views.thankyouPage, name='thankyou'),
    path('about-me/', views.aboutmePage, name='aboutme'),

**One of my templates I wish to link to viewblog page from ** ( I have tried to replace .id on my urls with .slug but this is what gives me the error.

<header>{% include 'navbardesktop.html' %}</header>
  <div class="blog-container">
    <h1 class="all-blog-title" id="all-blog-title" style="text-align: center;">All Blogs</h1>
      <div class="search">
        <form class="d-flex" method="POST" action="{% url 'searchblogs' %}">
          {% csrf_token %}
          <i class="fa fa-search"></i>
          <input type="text" class="form-control" placeholder="Search keyword" name="searched">
          <button id="search-btn" class="btn btn-secondary">Search</button>
    <hr id="blog-hr" style="width:50%; margin-left:25% !important; margin-right:25% !important;" />
    <div class="blog-post-container">
      <div class="dropdown">
        <button class="btn btn-secondary dropdown-toggle" type="button" data-bs-toggle="dropdown" aria-expanded="false">
          Blog List
        <ul class="dropdown-menu" style="background-color: #d6d6d6 ;">
          {% for post in posts %} {% if post.blog_published is True %}
          <li><a class="dropdown-item" href="{% url 'viewblog' %}">{{post.blog_title}}</a></li>
          {% endif %}
          {% endfor %}
        <script src="" integrity="sha384-kenU1KFdBIe4zVF0s0G1M5b4hcpxyD9F7jL+jjXkk+Q2h455rYXK/7HAuoJl+0I4" crossorigin="anonymous"></script>
      <div class="row">
        {% for post in posts %} {% if post.blog_published is True %}
          <div class="col-md-4" id="blog-col">
              <div class="blog-post">
                <div class="blog-content">
                      <img class="blog-img"src="{{post.blog_image.url}}"alt="My image"/>
                      <h2 class="blog-title">{{post.blog_title}}</h2>
                      <hr id="blog-hr" style="width: 90%" />
                      <article class="blog-article">
                      <a href="{% url 'viewblog' post.slug %}"class="btn btn-secondary"type="button"class="blog-button">Read More...</a>
                      <p class="blog-date">Posted on: {{post.blog_date}}</p>
              {% endif %} {% empty %}
              <h3>No Blog Uploads</h3>
              {% endfor %}

to debug just print the value of post.slug into the html page and you will see what is wrong. the "xxx" and "yyy" are just there to mark on the output clearly where some content shoult appear.

{% for post in posts %} 

xxx {{ post.slug }} xxx <br>
yyy {{ post.blog_title }} xxx <br>

{% endfor %}
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