Fix undefined method error

[FixRM rapid7#8340]

Author: wchen-r7

modules/auxiliary/scanner/http/dir_webdav_unicode_bypass.rb

@@ -164,7 +164,7 @@ def run_host(ip)
 						'data'		=> webdav_req + "\r\n\r\n",
 					}, 20)
 
-					if (res.code.to_i == 207)
+					if (res and res.code.to_i == 207)
 						print_status("\tFound vulnerable WebDAV Unicode bypass target #{wmap_base_url}#{tpath}%c0%af#{testfdir} #{res.code} (#{wmap_target_host})")
 
 						# Unable to use report_web_vuln as method is PROPFIND and is not part of allowed