If PATH_INFO is empty, the percent encoded path info is also empty. No need for complex computation.

Note this fixes an issue with libfcgi app not hosted as root url such as "/sub/app.fcgi".

library/server/wsf/src/wsf_request.e

@@ -838,6 +838,10 @@ feature -- Access: CGI meta parameters - 1.1
 		do
 			l_result := internal_percent_encoded_path_info
 			if l_result = Void then
+				pi := path_info
+				if pi.is_empty then
+					l_result := ""
+				else
 					r := request_uri
 					i := r.index_of ('?', 1)
 					if i > 0 then
@@ -845,7 +849,6 @@ feature -- Access: CGI meta parameters - 1.1
 					else
 						l_result := r.string
 					end
-				pi := path_info
 					i := 0
 					if pi.is_valid_as_string_8 then
 						i := l_result.substring_index (pi.to_string_8, 1)
@@ -884,6 +887,7 @@ feature -- Access: CGI meta parameters - 1.1
 							end
 						end
 					end
+				end
 				internal_percent_encoded_path_info := l_result
 			end
 			Result := l_result