Protect every access to the Table.u union using a nearby assert() or branch.

FossilOrigin-Name: 50e08338aed7ac0cee600098d2ecd4b3b7bfd31a597bb26773badf3d2e2582c8

src/insert.c

@@ -2219,7 +2219,8 @@ void sqlite3GenerateConstraintChecks(
     **
     ** This is not possible for ENABLE_PREUPDATE_HOOK builds, as the row
     ** must be explicitly deleted in order to ensure any pre-update hook
-    ** is invoked.  */ 
+    ** is invoked.  */
+    assert( IsOrdinaryTable(pTab) );
 #ifndef SQLITE_ENABLE_PREUPDATE_HOOK
     if( (ix==0 && pIdx->pNext==0)                   /* Condition 3 */
      && pPk==pIdx                                   /* Condition 2 */
@@ -2940,6 +2941,7 @@ static int xferOptimization(
   ** the extra complication to make this rule less restrictive is probably
   ** not worth the effort.  Ticket [6284df89debdfa61db8073e062908af0c9b6118e]
   */
+  assert( IsOrdinaryTable(pDest) );
   if( (db->flags & SQLITE_ForeignKeys)!=0 && pDest->u.tab.pFKey!=0 ){
     return 0;
   }