Fix missing typecast in DragHandler::onOrder() method #29540

Job	Run time
Unit (7.4, Phpunit)	1m 56s
Behat (8.1, Chrome)	5m 26s
Unit (7.4, Phpunit Lowest)	2m 9s
Docs	42s
Behat (8.1, Chrome Lowest)	5m 40s
Unit (8.0, Phpunit)	2m 10s
Behat (8.2, Chrome)	5m 26s
Unit (8.0, Phpunit Lowest)	2m 37s
Unit (8.1, Phpunit)	1m 59s
Unit (8.1, Phpunit Lowest)	2m 12s
Smoke (latest, Phpunit)	29s
Behat (8.2, Chrome Lowest)	5m 36s
Unit (8.2, Phpunit)	2m 20s
Smoke (latest, CodingStyle)	48s
Behat (8.3, Chrome)	13m 22s
Unit (8.2, Phpunit Lowest)	2m 3s
Behat (8.3, Chrome Lowest)	5m 32s
Unit (8.3, Phpunit)	4m 8s
Behat (latest, Firefox)	5m 35s
Unit (8.3, Phpunit Lowest)	2m 20s
Smoke (latest, StaticAnalysis)	39s
Behat (latest, Chrome Slow)	9m 23s
Unit (latest, Phpunit Burn)	5m 21s
Behat (latest, Firefox Slow)	7m 48s
	1h 35m 41s

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