fix: avoid panic when open fails

gorm.go

@@ -181,7 +181,7 @@ func Open(dialector Dialector, opts ...Option) (db *DB, err error) {
 		err = config.Dialector.Initialize(db)
 
 		if err != nil {
-			if db, err := db.DB(); err == nil {
+			if db, _ := db.DB(); db != nil {
 				_ = db.Close()
 			}
 		}

tests/gorm_test.go

@@ -3,9 +3,19 @@ package tests_test
 import (
 	"testing"
 
+	"gorm.io/driver/mysql"
+
 	"gorm.io/gorm"
 )
 
+func TestOpen(t *testing.T) {
+	dsn := "gorm:gorm@tcp(localhost:9910)/gorm?loc=Asia%2FHongKong" // invalid loc
+	_, err := gorm.Open(mysql.Open(dsn), &gorm.Config{})
+	if err == nil {
+		t.Fatalf("should returns error but got nil")
+	}
+}
+
 func TestReturningWithNullToZeroValues(t *testing.T) {
 	dialect := DB.Dialector.Name()
 	switch dialect {