[gimp/gimp-2-10] Issue #1662 - GIMP crashes while using cage transform when selection is active

[Michael Natterer <mitch src gnome org>]

commit af2a27f1c9d3c76e6100fa045e4447c26003e2ea
Author: Michael Natterer <mitch gimp org>
Date:   Tue Aug 7 20:05:07 2018 +0200

    Issue #1662 - GIMP crashes while using cage transform when selection is active
    
    Fixed by implementing Massimo's two findings:
    
    gimp_operation_cage_transform_process(): if aux_buf is NULL, bail out
    after initializing out_buf with identity vectors, fixes the crash.
    
    gimp_cage_tool_create_filter(): set the drawable filter's region to
    GIMP_FILTER_REGION_DRAWABLE, fixes offset when there is a selection.
    
    (cherry picked from commit 49dfc6143d66d10be4cd1f8ba288729342521f6a)

 app/operations/gimpoperationcagetransform.c | 3 +++
 app/tools/gimpcagetool.c                    | 1 +
 2 files changed, 4 insertions(+)
---
diff --git a/app/operations/gimpoperationcagetransform.c b/app/operations/gimpoperationcagetransform.c
index ebc9dc647e..f0467d5088 100644
--- a/app/operations/gimpoperationcagetransform.c
+++ b/app/operations/gimpoperationcagetransform.c
@@ -288,6 +288,9 @@ gimp_operation_cage_transform_process (GeglOperation       *operation,
         }
     }
 
+  if (! aux_buf)
+    return TRUE;
+
   gegl_operation_progress (operation, 0.0, "");
 
   /* pre-allocate memory outside of the loop */
diff --git a/app/tools/gimpcagetool.c b/app/tools/gimpcagetool.c
index 54bd9da2cc..c1065f5c39 100644
--- a/app/tools/gimpcagetool.c
+++ b/app/tools/gimpcagetool.c
@@ -1266,6 +1266,7 @@ gimp_cage_tool_create_filter (GimpCageTool *ct)
                                          _("Cage transform"),
                                          ct->render_node,
                                          GIMP_ICON_TOOL_CAGE);
+  gimp_drawable_filter_set_region (ct->filter, GIMP_FILTER_REGION_DRAWABLE);
 
   g_signal_connect (ct->filter, "flush",
                     G_CALLBACK (gimp_cage_tool_filter_flush),