fix(monitoring): guard against nil pointer in pooler PodMonitor template (#841)

* fix(monitoring): guard against nil pointer in pooler PodMonitor template

When a pooler defines `monitoring.enabled: true` without a `podMonitor`
sub-key, the template panics with a nil pointer error because Go
templates evaluate all arguments to `and` before calling the function.

Signed-off-by: Philippe Noël <philippemnoel@gmail.com>
Signed-off-by: Itay Grudev <itay+github.com@grudev.com>
Co-authored-by: Itay Grudev <itay@verito.digital>
Co-authored-by: Itay Grudev <itay+github.com@grudev.com>

Author: philippemnoel

charts/cluster/templates/podmonitor-pooler.yaml

@@ -1,6 +1,9 @@
 {{- range .Values.poolers }}
+{{- if .monitoring }}
+{{- if .monitoring.enabled }}
+{{- if .monitoring.podMonitor }}
+{{- if .monitoring.podMonitor.enabled }}
 ---
-{{- if and .monitoring .monitoring.enabled .monitoring.podMonitor.enabled }}
 apiVersion: monitoring.coreos.com/v1
 kind: PodMonitor
 metadata:
@@ -35,3 +38,6 @@ spec:
       {{- end }}
 {{- end }}
 {{- end }}
+{{- end }}
+{{- end }}
+{{- end }}