Fix Sidecar without image specification issue (#2977)

Co-authored-by: Oleg Nozdrachev <ovnozdrach@mts.ru>
Co-authored-by: Felix Kunde <felix-kunde@gmx.de>

pkg/cluster/k8sres.go

@@ -1303,6 +1303,9 @@ func (c *Cluster) generateStatefulSet(spec *acidv1.PostgresSpec) (*appsv1.Statef
 			c.logger.Warningf("initContainers specified but disabled in configuration - next statefulset creation would fail")
 		}
 		initContainers = spec.InitContainers
+		if err := c.validateContainers(initContainers); err != nil {
+			return nil, fmt.Errorf("invalid init containers: %v", err)
+		}
 	}
 
 	// backward compatible check for InitContainers
@@ -1455,6 +1458,10 @@ func (c *Cluster) generateStatefulSet(spec *acidv1.PostgresSpec) (*appsv1.Statef
 
 	sidecarContainers = patchSidecarContainers(sidecarContainers, volumeMounts, c.OpConfig.SuperUsername, c.credentialSecretName(c.OpConfig.SuperUsername))
 
+	if err := c.validateContainers(sidecarContainers); err != nil {
+		return nil, fmt.Errorf("invalid sidecar containers: %v", err)
+	}
+
 	tolerationSpec := tolerations(&spec.Tolerations, c.OpConfig.PodToleration)
 	effectivePodPriorityClassName := util.Coalesce(spec.PodPriorityClassName, c.OpConfig.PodPriorityClassName)
 
@@ -2592,3 +2599,15 @@ func ensurePath(file string, defaultDir string, defaultFile string) string {
 	}
 	return file
 }
+
+func (c *Cluster) validateContainers(containers []v1.Container) error {
+	for i, container := range containers {
+		if container.Name == "" {
+			return fmt.Errorf("container[%d]: name is required", i)
+		}
+		if container.Image == "" {
+			return fmt.Errorf("container '%v': image is required", container.Name)
+		}
+	}
+	return nil
+}