Merge branch 'hotfix/course_bugs_30-01-19' into 'master'

Добавление курса выдает 500

See merge request lilschool/site!258

apps/course/models.py

@@ -123,7 +123,7 @@ class Course(BaseModel, DeactivatedMixin):
         return str(self.id) + ' ' + self.title
 
     def save(self, *args, **kwargs):
-        if not self.slug:
+        if not self.slug and self.title:
             self.slug = slugify(unidecode(self.title[:90]))
         if self.slug:
             if self.slug.isdigit():