Fix panic in bench_test when database auth is not set.
Fix panic in bench_test when database auth is not set.

VividCortex/pq,bugreplaydev/pq,dongzerun/pq,jnewmano/pq,sammi/pq,bugreplaydev/pq,springning/pq,henrylee2cn/pq,amaniak/pq,flynn/pq,erichnascimento/pq,beni55/pq,everalbum/pq,johto/pq,ScriptRock/pq,ympons/pq,ld9999999999/pqpooling,lib/pq,jnewmano/pq,StabbyCutyou/pq,cbandy/go-pq,calebthompson/pq,stvp/pq,ympons/pq