fix: Fix a possible nil pointer exception on configuration reload

Thanks to @aolwas for the report

go.sum

@@ -59,8 +59,6 @@ github.com/go-playground/universal-translator v0.18.1 h1:Bcnm0ZwsGyWbCzImXv+pAJn
 github.com/go-playground/universal-translator v0.18.1/go.mod h1:xekY+UJKNuX9WP91TpwSH2VMlDf28Uj24BCp08ZFTUY=
 github.com/go-playground/validator/v10 v10.22.1 h1:40JcKH+bBNGFczGuoBYgX4I6m/i27HYW8P9FDk5PbgA=
 github.com/go-playground/validator/v10 v10.22.1/go.mod h1:dbuPbCMFw/DrkbEynArYaCwl3amGuJotoKCe95atGMM=
-github.com/go-resty/resty/v2 v2.15.2 h1:wLGqKU9l9tOIa2RyePoyu4ZUnDkUWfp2LZ0u6fMXExc=
-github.com/go-resty/resty/v2 v2.15.2/go.mod h1:0fHAoK7JoBy/Ch36N8VFeMsK7xQOHhvWaC3iOktwmIU=
 github.com/go-resty/resty/v2 v2.15.3 h1:bqff+hcqAflpiF591hhJzNdkRsFhlB96CYfBwSFvql8=
 github.com/go-resty/resty/v2 v2.15.3/go.mod h1:0fHAoK7JoBy/Ch36N8VFeMsK7xQOHhvWaC3iOktwmIU=
 github.com/gobwas/glob v0.2.3 h1:A4xDbljILXROh+kObIiy5kIaPYD8e96x1tgBhUI5J+Y=
@@ -177,8 +175,6 @@ go.etcd.io/bbolt v1.3.5/go.mod h1:G5EMThwa9y8QZGBClrRx5EY+Yw9kAhnjy3bSjsnlVTQ=
 go.uber.org/atomic v1.7.0/go.mod h1:fEN4uk6kAWBTFdckzkM89CLk9XfWZrxpCo0nPH17wJc=
 go.uber.org/atomic v1.11.0 h1:ZvwS0R+56ePWxUNi+Atn9dWONBPp/AUETXlHW0DxSjE=
 go.uber.org/atomic v1.11.0/go.mod h1:LUxbIzbOniOlMKjJjyPfpl4v+PKK2cNJn91OQbhoJI0=
-go.uber.org/mock v0.4.0 h1:VcM4ZOtdbR4f6VXfiOpwpVJDL6lCReaZ6mw31wqh7KU=
-go.uber.org/mock v0.4.0/go.mod h1:a6FSlNadKUHUa9IP5Vyt1zh4fC7uAwxMutEAscFbkZc=
 go.uber.org/mock v0.5.0 h1:KAMbZvZPyBPWgD14IrIQ38QCyjwpvVVV6K/bHl1IwQU=
 go.uber.org/mock v0.5.0/go.mod h1:ge71pBPLYDk7QIi1LupWxdAykm7KIEFchiOqd6z7qMM=
 go.uber.org/multierr v1.6.0/go.mod h1:cdWPpRnG4AhwMwsgIHip0KRBQjJy5kYEpYjJxpXp9iU=

pkg/s3-proxy/config/managerimpl.go

@@ -373,7 +373,10 @@ func loadAllCredentials(out *Config) ([]*CredentialConfig, error) {
 			}
 		}
 		// Load credentials for access key and secret key
-		if item.Bucket.Credentials != nil && item.Bucket.Credentials.AccessKey != nil && item.Bucket.Credentials.SecretKey != nil {
+		if item.Bucket != nil &&
+			item.Bucket.Credentials != nil &&
+			item.Bucket.Credentials.AccessKey != nil &&
+			item.Bucket.Credentials.SecretKey != nil {
 			// Manage access key
 			err := loadCredential(item.Bucket.Credentials.AccessKey)
 			if err != nil {