Fix mimir.rules.kubernetes panic on non-leader debug info retrieval (#3451)

* Fix mimir.rules.kubernetes to only return eventProcessor state if it exists

Author: TheoBrigitte

CHANGELOG.md

@@ -12,6 +12,8 @@ v1.8.3
 
 ### Bugfixes
 
+- Fix `mimir.rules.kubernetes` panic on non-leader debug info retrieval (@TheoBrigitte)
+
 - Fix `loki.source.file` race condition that often lead to panic when using `decompression`. (@kalleep)
 
 v1.8.2

internal/component/mimir/rules/kubernetes/debug.go

@@ -23,6 +23,10 @@ type DebugMimirNamespace struct {
 func (c *Component) DebugInfo() interface{} {
 	var output DebugInfo
 
+	if c.eventProcessor == nil {
+		return output
+	}
+
 	currentState := c.eventProcessor.getMimirState()
 	for namespace := range currentState {
 		if !isManagedMimirNamespace(c.args.MimirNameSpacePrefix, namespace) {