[gimp/gimp-2-10] Fix a GUI bug in HEIF/AVIF export dialog.

[Jehan <jehanp src gnome org>]

commit 1202c2555bc3b597deda14cae0a0616039617f29
Author: Daniel Novomesky <dnovomesky gmail com>
Date:   Sat Oct 10 14:19:53 2020 +0200

    Fix a GUI bug in HEIF/AVIF export dialog.

 plug-ins/common/file-heif.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/plug-ins/common/file-heif.c b/plug-ins/common/file-heif.c
index 543994ce13..06af14d018 100644
--- a/plug-ins/common/file-heif.c
+++ b/plug-ins/common/file-heif.c
@@ -1998,7 +1998,7 @@ save_dialog (SaveParams  *params,
   gtk_range_set_value (GTK_RANGE (quality_slider), params->quality);
   gtk_toggle_button_set_active (GTK_TOGGLE_BUTTON (lossless_button),
                                 params->lossless);
-  gtk_widget_set_sensitive (quality_slider, !params->lossless);
+  gtk_widget_set_sensitive (hbox, !params->lossless);
   gtk_label_set_mnemonic_widget (GTK_LABEL (label), quality_slider);
 
   g_signal_connect (lossless_button, "toggled",