Fixed #29648 -- Fixed crash when using subqueries inside datetime truncation functions.

tests/db_functions/models.py

@@ -32,6 +32,7 @@ class Fan(models.Model):
     name = models.CharField(max_length=50)
     age = models.PositiveSmallIntegerField(default=30)
     author = models.ForeignKey(Author, models.CASCADE, related_name='fans')
+    fan_since = models.DateTimeField(null=True, blank=True)
 
     def __str__(self):
         return self.name