empty sslkey-file causes panic in `pgx.Connect`

[gabor]

Describe the bug
if i use an empty-file as the sslkey, pgx will panic.

To Reproduce
create an empty file named key.key
then run this program:

package main

import (
	"context"

	"github.com/jackc/pgx/v5"
)

func main() {
	pgx.Connect(context.Background(), "host=localhost sslkey=key.key sslcert=key.crt")
}

Expected behavior

pgx.Connect should return an error, if the sslkey is an empty file, it should not panic.

Actual behavior
pgx.Connect panics when sslkey is an empty file.
A clear and concise description of what actually happened.

Version

• Go: go version go1.22.0 darwin/arm64
• PostgreSQL: postgres is not running
• pgx: v5.5.3

Additional context
i think the problem is here:

pgx/pgconn/config.go

Lines 723 to 728 in 5c63f64

	block, _ := pem.Decode(buf)
	var pemKey []byte
	var decryptedKey []byte
	var decryptedError error
	// If PEM is encrypted, attempt to decrypt using pass phrase
	if x509.IsEncryptedPEMBlock(block) {

pem.Decode() will return an error, but it is not checked. then x509.IsEncryptedPEMBlock() panics.

[jackc]

Fixed in 8896bd6.