dont panic on empty SRV segments (#5173)

Signed-off-by: Chris O'Haver <cohaver@infoblox.com>

plugin/kubernetes/parse.go

@@ -82,6 +82,9 @@ func parseRequest(name, zone string) (r recordRequest, err error) {
 
 // stripUnderscore removes a prefixed underscore from s.
 func stripUnderscore(s string) string {
+	if len(s) == 0 {
+		return s
+	}
 	if s[0] != '_' {
 		return s
 	}

plugin/kubernetes/parse_test.go

@@ -23,6 +23,8 @@ func TestParseRequest(t *testing.T) {
 		{"svc.inter.webs.tests.", "....."},
 		// bare pod type
 		{"pod.inter.webs.tests.", "....."},
+		// SRV request with empty segments
+		{"..webs.mynamespace.svc.inter.webs.tests.", "...webs.mynamespace.svc"},
 	}
 	for i, tc := range tests {
 		m := new(dns.Msg)