[gimp] app: in GimpProjection, avoid invalidating preview on flush while rendering

[Ell <ell src gnome org>]

commit 49bbf139113fbc5581e4160160416da1feb52524
Author: Ell <ell_se yahoo com>
Date:   Wed Sep 4 12:51:27 2019 +0300

    app: in GimpProjection, avoid invalidating preview on flush while rendering
    
    In GimpProjection, avoid erroneously invalidating the projectable's
    preview when flushing the projection and there's nothing to be
    flushed, if the chunk renderer is still running, and hence the
    projection is not fully rendered yet.

 app/core/gimpprojection.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/app/core/gimpprojection.c b/app/core/gimpprojection.c
index d1ec176c6e..30374374c6 100644
--- a/app/core/gimpprojection.c
+++ b/app/core/gimpprojection.c
@@ -676,7 +676,7 @@ gimp_projection_flush_whenever (GimpProjection *proj,
           gimp_projection_chunk_render_start (proj);
         }
     }
-  else if (! now && proj->priv->invalidate_preview)
+  else if (! now && ! proj->priv->iter && proj->priv->invalidate_preview)
     {
       /* invalidate the preview here since it is constructed from
        * the projection