[gimp] app: in gimp_filter_tool_get_drawable_area(), don't return empty area

[Ell <ell src gnome org>]

commit 428ee0e2ad9327145860787628aebb159a19a9b9
Author: Ell <ell_se yahoo com>
Date:   Thu Jun 6 02:56:23 2019 -0400

    app: in gimp_filter_tool_get_drawable_area(), don't return empty area
    
    In gimp_filter_tool_get_drawable_area(), when the image mask
    doesn't intersect the drawable, return a minimal area, instead of
    an empty/invalid area.

 app/tools/gimpfiltertool.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)
---
diff --git a/app/tools/gimpfiltertool.c b/app/tools/gimpfiltertool.c
index 58cf0b3b94..432399f8b6 100644
--- a/app/tools/gimpfiltertool.c
+++ b/app/tools/gimpfiltertool.c
@@ -1801,11 +1801,17 @@ gimp_filter_tool_get_drawable_area (GimpFilterTool *filter_tool,
       switch (options->region)
         {
         case GIMP_FILTER_REGION_SELECTION:
-          gimp_item_mask_intersect (GIMP_ITEM (drawable),
-                                    &drawable_area->x,
-                                    &drawable_area->y,
-                                    &drawable_area->width,
-                                    &drawable_area->height);
+          if (! gimp_item_mask_intersect (GIMP_ITEM (drawable),
+                                          &drawable_area->x,
+                                          &drawable_area->y,
+                                          &drawable_area->width,
+                                          &drawable_area->height))
+            {
+              drawable_area->x      = 0;
+              drawable_area->y      = 0;
+              drawable_area->width  = 1;
+              drawable_area->height = 1;
+            }
           break;
 
         case GIMP_FILTER_REGION_DRAWABLE: