ipcache: Error out from InjectLabels if Checker is nil

[ upstream commit 078c052 ]

K8s cache is not fully synced also when k8sSyncedChecker is still nil.

Found during code inspection, not sure if this can manifest as a bug on
runtime.

Fixes: #17823
Signed-off-by: Jarno Rajahalme <jarno@isovalent.com>
Signed-off-by: Gilberto Bertin <jibi@cilium.io>

pkg/ipcache/metadata.go

@@ -90,8 +90,7 @@ func InjectLabels(src source.Source, updater identityUpdater, triggerer policyTr
 		return ErrLocalIdentityAllocatorUninitialized
 	}
 
-	if IPIdentityCache.k8sSyncedChecker != nil &&
-		!IPIdentityCache.k8sSyncedChecker.K8sCacheIsSynced() {
+	if IPIdentityCache.k8sSyncedChecker == nil || !IPIdentityCache.k8sSyncedChecker.K8sCacheIsSynced() {
 		return errors.New("k8s cache not fully synced")
 	}