Skip Formatting For NIL Secret (#18163)

* Skip formatting for a nil secret data

* Same change for put

* Add changelog

* update changelog

* modify filtered output

changelog/18163.txt

@@ -0,0 +1,3 @@
+```release-note:bug
+cli/kv: skip formatting of nil secrets for patch and put with field parameter set
+```

command/kv_patch.go

@@ -252,6 +252,14 @@ func (c *KVPatchCommand) Run(args []string) int {
 	if code != 0 {
 		return code
 	}
+	if secret == nil {
+		// Don't output anything if there's no secret
+		return 0
+	}
+
+	if c.flagField != "" {
+		return PrintRawField(c.UI, secret, c.flagField)
+	}
 
 	if Format(c.UI) == "table" {
 		outputPath(c.UI, fullPath, "Secret Path")