middleware: fix waitForLeader in redirector panic #20944

Job	Run time
chunks (1, Unit Test(1))	5m 16s
chunks (2, Unit Test(2))	3m 56s
chunks (3, Unit Test(3))	4m 43s
chunks (4, Tests(1))	4m 54s
chunks (5, Tests(2))	4m 57s
chunks (6, Tools Test)	5m 37s
chunks (7, Client Integration Test)	4m 33s
chunks (8, TSO Integration Test)	4m 49s
chunks (9, MicroService Integration(!TSO))	3m 31s
chunks (10, MicroService Integration(TSO))	5m 6s
report-coverage	14s
	47m 36s

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