fixing string:substring built-in

RELEASE

@@ -1,5 +1,6 @@
                                   EYE release
 
+v10.20.4 (2024-09-04) fixing string:substring built-in
 v10.20.3 (2024-09-04) further fixing issue https://github.com/eyereasoner/eye/issues/108
 v10.20.2 (2024-09-04) further fixing issue https://github.com/eyereasoner/eye/issues/115
 v10.20.1 (2024-09-03) fixing log:callWithCut built-in

VERSION

@@ -1 +1 @@
-10.20.3
+10.20.4

eye.pl

@@ -22,7 +22,7 @@
 :- catch(use_module(library(process)), _, true).
 :- catch(use_module(library(http/http_open)), _, true).
 
-version_info('EYE v10.20.3 (2024-09-04)').
+version_info('EYE v10.20.4 (2024-09-04)').
 
 license_info('MIT License
 
@@ -8767,7 +8767,8 @@
         (   ground([A, B])
         ),
         (   getint(B, I),
-            sub_atom(A, 0, E, 0, _),
+            escape_atom(A, Ae),
+            sub_atom(Ae, 0, E, 0, _),
             J is E-I+1,
             (   I < 1
             ->  G is 0,
@@ -8776,9 +8777,8 @@
                 H is J
             ),
             (   H < 0
-            ->  D = []
-            ;   escape_atom(A, Ae),
-                escape_atom(D, De),
+            ->  D = ''
+            ;   escape_atom(D, De),
                 sub_atom(Ae, G, H, _, De)
             )
         )
@@ -9186,7 +9186,7 @@
                 H is J
             ),
             (   H < 0
-            ->  D = []
+            ->  D = ''
             ;   sub_atom(A, G, H, _, D)
             )
         )