[gimp] Bug 795418 - Gimp 'critical error' when running luminosity masks script

[Michael Natterer <mitch src gnome org>]

commit 8be37da0128ad319778737cafcb824d976cba66a
Author: Michael Natterer <mitch gimp org>
Date:   Sat Apr 21 10:38:55 2018 +0200

    Bug 795418 - Gimp 'critical error' when running luminosity masks script
    
    In the gimp-channel-combine-masks PDB wrapper, only push an undo step
    if the modified channel is attached to an image. It's a completely
    reasonable use case to combine unattached channels.

 app/pdb/channel-cmds.c |    4 +++-
 pdb/groups/channel.pdb |    4 +++-
 2 files changed, 6 insertions(+), 2 deletions(-)
---
diff --git a/app/pdb/channel-cmds.c b/app/pdb/channel-cmds.c
index a80c6f5..b1db2bd 100644
--- a/app/pdb/channel-cmds.c
+++ b/app/pdb/channel-cmds.c
@@ -195,7 +195,9 @@ channel_combine_masks_invoker (GimpProcedure         *procedure,
 
   if (success)
     {
-      gimp_channel_push_undo (channel1, _("Combine Masks"));
+      if (gimp_item_is_attached (GIMP_ITEM (channel1)))
+        gimp_channel_push_undo (channel1, _("Combine Masks"));
+
       gimp_channel_combine_mask (channel1, channel2, operation, offx, offy);
     }
 
diff --git a/pdb/groups/channel.pdb b/pdb/groups/channel.pdb
index 0d0ae94..c7dd504 100644
--- a/pdb/groups/channel.pdb
+++ b/pdb/groups/channel.pdb
@@ -143,7 +143,9 @@ HELP
         headers => [ qw("core/gimpchannel-combine.h" "gimp-intl.h") ],
         code => <<'CODE'
 {
-  gimp_channel_push_undo (channel1, _("Combine Masks"));
+  if (gimp_item_is_attached (GIMP_ITEM (channel1)))
+    gimp_channel_push_undo (channel1, _("Combine Masks"));
+
   gimp_channel_combine_mask (channel1, channel2, operation, offx, offy);
 }
 CODE