[gimp] app: avoid flushing bufferless projections

[Ell <ell src gnome org>]

commit b07f8102738d8225c1e77e6b4f68ae12468d8a2b
Author: Ell <ell_se yahoo com>
Date:   Wed Nov 28 12:53:52 2018 -0500

    app: avoid flushing bufferless projections
    
    Don't needlessly flush projections whose buffer hasn't been
    allocated yet.  This can happen when opening an image, in which
    case the image is flushed before its projection has a buffer.

 app/core/gimpprojection.c | 3 +++
 1 file changed, 3 insertions(+)
---
diff --git a/app/core/gimpprojection.c b/app/core/gimpprojection.c
index 158cb48231..2a8264a9d8 100644
--- a/app/core/gimpprojection.c
+++ b/app/core/gimpprojection.c
@@ -785,6 +785,9 @@ static void
 gimp_projection_flush_whenever (GimpProjection *proj,
                                 gboolean        now)
 {
+  if (! proj->priv->buffer)
+    return;
+
   if (proj->priv->update_region)
     {
       if (now)  /* Synchronous */