libc/iconv: Detect CES handler loading failure

Fix the code checking for character set loading failure so that
it checks the return value from the init function.

Signed-off-by: Keith Packard <keithp@keithp.com>

newlib/libc/iconv/ces/euc.c

@@ -306,7 +306,7 @@ ok:
       data->data[i] = _iconv_to_ucs_ces_handlers_table.init (
                                                         rptr,
                                                         data->desc[i].csname);
-      if (data->data == NULL)
+      if (data->data[i] == NULL)
         goto error;
     }