Fix undefined method error

[FixRM rapid7#8324]

Author: wchen-r7

modules/auxiliary/scanner/oracle/spy_sid.rb

@@ -42,7 +42,7 @@ def run_host(ip)
 				'version' => '1.1',
 			}, 5)
 
-			if ( res.body =~ /SERVICE_NAME=/ )
+			if res and res.body =~ /SERVICE_NAME=/
 				select(nil,nil,nil,2)
 				sid = res.body.scan(/SERVICE_NAME=([^\)]+)/)
 					report_note(