Handle exception generated when the spider process hands http-backup-finder a URL that is only a hostname. When url.parse processes this value on line 107 of http-backup-finder it returns nil for the .path property.

http-backup-finder.nse:107: attempt to index field 'path' (a nil value)
stack traceback:

Addressed this by setting nil .path values to '/'.  Tested with sites with and without backup files.  Verified that duplicate results were not returned.

scripts/http-backup-finder.nse

@@ -102,6 +102,11 @@ action = function(host, port)
 
 		-- parse the returned url
 		local parsed = url.parse(tostring(r.url))
+    
+		-- handle case where only hostname was provided
+		if ( parsed.path == nil ) then
+			parsed.path = '/'
+		end
 		
 		-- only pursue links that have something looking as a file
 		if ( parsed.path:match(".*%.*.$") ) then