Make sure res has value before passing it on to exec_php

Author: sinn3r

modules/exploits/unix/webapp/projectpier_upload_exec.rb

@@ -164,6 +164,11 @@ def exploit
 		print_status("#{@peer} - Uploading PHP payload (#{p.length.to_s} bytes)...")
 		res = upload_php(base, php_fname, p, folder_name)
 
+		if not res
+			print_error("#{@peer} - No response from server")
+			return
+		end
+
 		print_status("#{@peer} - Executing '#{php_fname}'...")
 		exec_php(base, res)
 	end