cgidmap: do not panic if cri is not enabled

cgidmap requires cri for pod association to work with existing pods.
Currently, if cri is not enabled the cgidmap code will panic:

E0904 10:02:54.892524   22765 runtime.go:79] Observed a panic: "invalid memory address or nil pointer dereference" (runtime error: invalid memory address or nil pointer dereference)
goroutine 13 [running]:
k8s.io/apimachinery/pkg/util/runtime.logPanic({0x276f260, 0x4a09c00})
        /home/kkourt/src/tetragon/vendor/k8s.io/apimachinery/pkg/util/runtime/runtime.go:75 +0x85
k8s.io/apimachinery/pkg/util/runtime.HandleCrash({0x0, 0x0, 0xc004fd3340?})
        /home/kkourt/src/tetragon/vendor/k8s.io/apimachinery/pkg/util/runtime/runtime.go:49 +0x6b
panic({0x276f260?, 0x4a09c00?})
        /opt/go/src/runtime/panic.go:770 +0x132
github.com/cilium/tetragon/pkg/cgidmap.(*criResolver).enqeue(0x0, {0xc005434f20, 0xc004fdfb28?, 0x40?})

This commit adds a nil check to avoid the panic and issues a warning if
cri is not enabled but cgidmap is.

Signed-off-by: Kornilios Kourtis <[email protected]>

pkg/cgidmap/cgidmap.go

@@ -91,6 +91,8 @@ func newMap() (*cgidm, error) {
 	var criResolver *criResolver
 	if option.Config.EnableCRI {
 		criResolver = newCriResolver(m)
+	} else {
+		logger.GetLogger().Warn("cgidmap is enabled but cri is not. This means that pod association will not work for existing pods. You can enable cri using --enable-cri")
 	}
 	m.criResolver = criResolver
 	return m, nil
@@ -234,7 +236,9 @@ func (m *cgidm) Update(podID PodID, contIDs []ContainerID) {
 			contID: id,
 		})
 	}
-	m.criResolver.enqeue(unmappedIDs)
+	if m.criResolver != nil {
+		m.criResolver.enqeue(unmappedIDs)
+	}
 }
 
 // Global state