Fix #13864: Removed database error raised when force_update is requsted on save of an inherited model with no fields of its own. Thanks fva, gregmuellegger, and markb1.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@17088 bcc190cf-cafb-0310-a4f2-bffc1f526a37

tests/modeltests/force_insert_update/models.py

@@ -9,6 +9,16 @@ class Counter(models.Model):
     name = models.CharField(max_length = 10)
     value = models.IntegerField()
 
+class InheritedCounter(Counter):
+    tag = models.CharField(max_length=10)
+
+class ProxyCounter(Counter):
+    class Meta:
+        proxy = True
+
+class SubCounter(Counter):
+    pass
+
 class WithCustomPK(models.Model):
     name = models.IntegerField(primary_key=True)
     value = models.IntegerField()