trx_start_for_ddl_low(): Remove dangerous error-tolerance

A dictionary transaction must be flagged as such before it has generated
any undo log records. This is because trx_undo_assign_undo() will mark
the transaction as a dictionary transaction in the undo log header
right before the very first undo log record is being written.

storage/innobase/trx/trx0trx.cc

@@ -3014,15 +3014,6 @@ trx_start_for_ddl_low(
 		return;
 
 	case TRX_STATE_ACTIVE:
-
-		/* We have this start if not started idiom, therefore we
-		can't add stronger checks here. */
-		trx->ddl = true;
-
-		ut_ad(trx->dict_operation != TRX_DICT_OP_NONE);
-		ut_ad(trx->will_lock > 0);
-		return;
-
 	case TRX_STATE_PREPARED:
 	case TRX_STATE_COMMITTED_IN_MEMORY:
 		break;