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

@@ -838,49 +838,53 @@ feature -- Access: CGI meta parameters - 1.1
 		do
 			l_result := internal_percent_encoded_path_info
 			if l_result = Void then
-				r := request_uri
-				i := r.index_of ('?', 1)
-				if i > 0 then
-					l_result := r.substring (1, i - 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)
+				if pi.is_empty then
+					l_result := ""
+				else
+					r := request_uri
+					i := r.index_of ('?', 1)
 					if i > 0 then
-							-- Path info is included in REQUEST_URI
-							-- so let's get the percent encoded path info from request uri.
-						l_result := l_result.substring (i, l_result.count)
-					end
-				end
-					--| here "i = 0" means request_uri does not start with `path_info',
-					--| thus let's compute it from `script_name'.
-				if i = 0 and attached script_name as s then
-					if l_result.starts_with (s) then
-						l_result := l_result.substring (s.count + 1, l_result.count)
+						l_result := r.substring (1, i - 1)
 					else
-							--| Handle Rewrite url engine, to have clean path
-						from
-							i := 1
-							m := l_result.count
-							n := s.count
-						until
-							i > m or i > n or l_result[i] /= s[i]
-						loop
-							if l_result[i] = '/' then
-								spos := i
-							end
-							i := i + 1
+						l_result := r.string
+					end
+					i := 0
+					if pi.is_valid_as_string_8 then
+						i := l_result.substring_index (pi.to_string_8, 1)
+						if i > 0 then
+								-- Path info is included in REQUEST_URI
+								-- so let's get the percent encoded path info from request uri.
+							l_result := l_result.substring (i, l_result.count)
 						end
-						if i > 1 then
-							if l_result[i-1] = '/' then
-								i := i -1
-							elseif spos > 0 then
-								i := spos
+					end
+						--| here "i = 0" means request_uri does not start with `path_info',
+						--| thus let's compute it from `script_name'.
+					if i = 0 and attached script_name as s then
+						if l_result.starts_with (s) then
+							l_result := l_result.substring (s.count + 1, l_result.count)
+						else
+								--| Handle Rewrite url engine, to have clean path
+							from
+								i := 1
+								m := l_result.count
+								n := s.count
+							until
+								i > m or i > n or l_result[i] /= s[i]
+							loop
+								if l_result[i] = '/' then
+									spos := i
+								end
+								i := i + 1
+							end
+							if i > 1 then
+								if l_result[i-1] = '/' then
+									i := i -1
+								elseif spos > 0 then
+									i := spos
+								end
+								l_result := l_result.substring (i, m)
 							end
-							l_result := l_result.substring (i, m)
 						end
 					end
 				end