[gimp] app: fix memory leak reported by Massimo.

[Jehan <jehanp src gnome org>]

commit 4336b7a8e34b604ef9bb1e7b6ec3288f5ff4b179
Author: Jehan <jehan girinstud io>
Date:   Mon Aug 16 18:57:21 2021 +0200

    app: fix memory leak reported by Massimo.

 app/core/gimppickable-contiguous-region.cc | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)
---
diff --git a/app/core/gimppickable-contiguous-region.cc b/app/core/gimppickable-contiguous-region.cc
index ddab72c837..37fbbca5e8 100644
--- a/app/core/gimppickable-contiguous-region.cc
+++ b/app/core/gimppickable-contiguous-region.cc
@@ -540,8 +540,11 @@ gimp_pickable_contiguous_region_by_line_art (GimpPickable *pickable,
             {
               mask[c->x + c->y * width] = 1.0;
               if (c->level >= line_art_max_grow)
-                /* Do not overflood under line arts. */
-                continue;
+                {
+                  /* Do not overflood under line arts. */
+                  g_free (c);
+                  continue;
+                }
               if (c->x > 0)
                 {
                   nx = c->x - 1;