io.gi: slight formatting tweak

Author: wilfwilson

gap/io.gi

@@ -1238,8 +1238,7 @@ function(s)
     # digraph definition line
     if first_char = 'p' then
       if IsBound(vertices) or Length(split) <> 4 or split[2] <> "edge" then
-        ErrorNoReturn("the format of the string <s>",
-                             " cannot be determined");
+        ErrorNoReturn("the format of the string <s> cannot be determined");
       fi;
       nr_vertices     := int_from_string(split[3]);
       vertices        := [1 .. nr_vertices];