adjust functor to move by dfa so that we cannot go to the last char of the file if (last char is a newline and is preceded by a non-newline), but otherwise we can go to the last char of the file.

fcore/cursor.sml

@@ -737,4 +737,9 @@ struct
           end
       | [] => true
     end
+
+  (* Prerequisite: lineGap is moved to cursorIdx *)
+  fun isOnNewlineAfterChr (buffer, cursorIdx) =
+    cursorIdx > 0 andalso not (isPrevChrStartOfLine (buffer, cursorIdx))
+    andalso isCursorAtStartOfLine (buffer, cursorIdx)
 end