fix(meshtrafficpermission): nil pointer for autoreachableservice when no top targetRef (backport of #12152) #9590

Job	Run time
check	10m 20s
test	3m 2s
gen_e2e_matrix	1s
test_e2e	0s
test_e2e_env (kubernetes, v1.28.1-k3s1, amd64, 1, flannel, false) / e2e (0)	5m 33s
test_e2e_env (multizone, v1.28.1-k3s1, amd64, 1, flannel, false) / e2e (0)	4m 25s
test_e2e_env (universal, kind, amd64, 1, flannel, false) / e2e (0)	4m 29s
distributions	3s
	27m 53s

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