allowed course foreignkey in Assignments app to be nullable

assignments/models.py

@@ -10,7 +10,7 @@ class Course(models.Model):
         return self.course_title
 
 class Assignment(models.Model):
-    course = models.ForeignKey(Course, on_delete=models.CASCADE,default="1")
+    course = models.ForeignKey(Course, on_delete=models.CASCADE,default=None,null=True,blank=True)
     name = models.CharField(max_length=100)
     description = models.CharField(max_length=500)
     max_points = models.IntegerField()