Panic when excluding fluentd

[lander2k2]

Describe the bug:
When I submit a Logging resource with spec.fluentd omitted, the controller manger panics

Expected behaviour:
For the logging operator to deploy fluent-bit only.

Steps to reproduce the bug:

1. remove the spec.fluentd block from a Logging manifest and create it.

Additional context:
none

Environment details:

• Kubernetes version: v1.19.7
• Cloud-provider/provisioner: AWS
• logging-operator version: 3.15.0
• Install method: Helm
• Logs from the controller:

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x1b0 pc=0x15d2d31]

goroutine 525 [running]:
github.com/banzaicloud/logging-operator/pkg/sdk/api/v1beta1.(*Logging).SetDefaults(0xc000d894a0, 0x1bea078, 0xc000853b90)
        /workspace/pkg/sdk/api/v1beta1/logging_types.go:295 +0x691
github.com/banzaicloud/logging-operator/controllers.(*LoggingReconciler).Reconcile(0xc0000becc0, 0x1bea078, 0xc000853b90, 0x0
, 0x0, 0xc000875ec0, 0xf, 0xc000853b90, 0xc000030000, 0x186b040, ...)
        /workspace/controllers/logging_controller.go:84 +0x245
sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).reconcileHandler(0xc00023d040, 0x1be9fd0, 0xc0002e3b80,
0x182b5a0, 0xc000bfe220)
        /go/pkg/mod/sigs.k8s.io/[email protected]/pkg/internal/controller/controller.go:298 +0x30d
sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).processNextWorkItem(0xc00023d040, 0x1be9fd0, 0xc0002e3b8
0, 0xc00092bf00)
        /go/pkg/mod/sigs.k8s.io/[email protected]/pkg/internal/controller/controller.go:253 +0x205
sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).Start.func2.2(0xc0004942d0, 0xc00023d040, 0x1be9fd0, 0xc
0002e3b80)
        /go/pkg/mod/sigs.k8s.io/[email protected]/pkg/internal/controller/controller.go:214 +0x6b
created by sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).Start.func2
        /go/pkg/mod/sigs.k8s.io/[email protected]/pkg/internal/controller/controller.go:210 +0x425

• Resource definition (possibly in YAML format) that caused the issue, without sensitive data:

apiVersion: logging.banzaicloud.io/v1beta1
kind: Logging
metadata:
  name: bug-example
spec:
  controlNamespace: logging-system
  fluentbit: {}

/kind bug

[lander2k2]

Also just noticed that when this panic is resolved, another emerges...

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x1d4 pc=0x13b460c]

goroutine 542 [running]:
github.com/banzaicloud/logging-operator/pkg/resources/fluentbit.(*Reconciler).configSecret(0xc001330c00)
        /home/bruce/Projects/src/github.com/banzaicloud/logging-operator/pkg/resources/fluentbit/configsecret.go:166 +0x74c
github.com/banzaicloud/logging-operator/pkg/resources/fluentbit.(*Reconciler).Reconcile(0xc001330c00)
        /home/bruce/Projects/src/github.com/banzaicloud/logging-operator/pkg/resources/fluentbit/fluentbit.go:96 +0x3a9
github.com/banzaicloud/logging-operator/controllers.(*LoggingReconciler).Reconcile(0xc00019fb80, {0x1947318, 0xc000b56900}, {{{0x0, 0x0}, {0xc000a31bb0, 0xb}}})
        /home/bruce/Projects/src/github.com/banzaicloud/logging-operator/controllers/logging_controller.go:128 +0xc65
sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).reconcileHandler(0xc0002912c0, {0x1947270, 0xc0003b6b00}, {0x15b7fe0, 0xc00019e000})
        /home/bruce/go/pkg/mod/sigs.k8s.io/[email protected]/pkg/internal/controller/controller.go:298 +0x303
sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).processNextWorkItem(0xc0002912c0, {0x1947270, 0xc0003b6b00})
        /home/bruce/go/pkg/mod/sigs.k8s.io/[email protected]/pkg/internal/controller/controller.go:253 +0x205
sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).Start.func2.2()
        /home/bruce/go/pkg/mod/sigs.k8s.io/[email protected]/pkg/internal/controller/controller.go:214 +0x85
created by sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).Start.func2
        /home/bruce/go/pkg/mod/sigs.k8s.io/[email protected]/pkg/internal/controller/controller.go:210 +0x354
exit status 2

[lander2k2]

New error was due to fluentd values being referenced for fluentbit's config secret. That has also been addressed in the linked PR.