EVP shake_ctrl(): add missing NULL evp_ctx check #1146

Job	Run time
run-checker (no-cmp)	7m 26s
run-checker (no-cms)	8m 44s
run-checker (no-dgram)	6m 59s
run-checker (no-dh)	7m 1s
run-checker (no-dtls)	7m 40s
run-checker (no-ec)	6m 30s
run-checker (no-ec2m)	7m 18s
run-checker (no-ecx)	7m 6s
run-checker (no-http)	10m 5s
run-checker (no-legacy)	8m 57s
run-checker (no-sock)	8m 16s
run-checker (enable-ssl-trace)	7m 17s
run-checker (no-threads)	9m 30s
run-checker (no-thread-pool)	7m 33s
run-checker (no-default-thread-pool)	7m 35s
run-checker (no-tls)	6m 58s
run-checker (no-tls1_2)	8m 37s
run-checker (no-tls1_3)	6m 50s
run-checker (enable-trace enable-fips)	8m 31s
run-checker (no-ui)	7m 39s
run-checker (no-quic)	6m 58s
	2h 43m 30s

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