bash script outputs "cannot make pipe for process substitution: Too many open files"

Issue

A pipe fd leak occurred in Process Substitution of bash script. As a result, bash script outputs the following message.

./test.sh: cannot make pipe for process substitution: Too many open files

Execute the following script to reproduce:

#!/bin/bash
sub(){
while :
do
/bin/true <(/bin/true)
done
}

sub
exit