[gimp] app: avoid allocating empty tempbuf for drawable previews

[Ell <ell src gnome org>]

commit 963322fdd4c4b99520c909cf215191776ecfb6d1
Author: Ell <ell_se yahoo com>
Date:   Sat Nov 3 04:28:15 2018 -0400

    app: avoid allocating empty tempbuf for drawable previews
    
    In gimp_view_renderer_drawable_render(), make sure the preview size
    is always at least 1x1.
    
    Fixes commit 8009ea342a22ad5e9fa7373f4031b407c41f03cb.

 app/widgets/gimpviewrendererdrawable.c | 3 +++
 1 file changed, 3 insertions(+)
---
diff --git a/app/widgets/gimpviewrendererdrawable.c b/app/widgets/gimpviewrendererdrawable.c
index 4368a74a0c..d8803298c5 100644
--- a/app/widgets/gimpviewrendererdrawable.c
+++ b/app/widgets/gimpviewrendererdrawable.c
@@ -275,6 +275,9 @@ gimp_view_renderer_drawable_render (GimpViewRenderer *renderer,
       dst_height = view_height;
     }
 
+  dst_width  = MAX (dst_width,  1);
+  dst_height = MAX (dst_height, 1);
+
   if (! empty)
     {
       async = gimp_drawable_get_sub_preview_async (drawable,