Make sure rendering config produces valid config
Fixes
@@ -1278,7 +1278,7 @@ func (a *RelabelAction) UnmarshalYAML(unmarshal func(interface{}) error) error {
type RelabelConfig struct {
// A list of labels from which values are taken and concatenated
// with the configured separator in order.
- SourceLabels model.LabelNames `yaml:"source_labels,flow"`
+ SourceLabels model.LabelNames `yaml:"source_labels,flow,omitempty"`
// Separator is the string between concatenated values from the source labels.
Separator string `yaml:"separator,omitempty"`
// Regex against which the concatenation is matched.
