[gtk] gl renderer: Ref transform before using it

[Timm Bäder <baedert src gnome org>]

commit efe9bba343f0ca839bb134fcc46bacd54b247a6a
Author: Timm Bäder <mail baedert org>
Date:   Mon Jun 3 15:54:25 2019 +0200

    gl renderer: Ref transform before using it
    
    Fixes #1929

 gsk/gl/gskglrenderops.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
---
diff --git a/gsk/gl/gskglrenderops.c b/gsk/gl/gskglrenderops.c
index df3760d32e..764c2eb645 100644
--- a/gsk/gl/gskglrenderops.c
+++ b/gsk/gl/gskglrenderops.c
@@ -423,7 +423,8 @@ ops_push_modelview (RenderOpBuilder *builder,
       cur = &g_array_index (builder->mv_stack, MatrixStackEntry, builder->mv_stack->len - 2);
       /* Multiply given matrix with current modelview */
 
-      t = gsk_transform_translate (cur->transform, &(graphene_point_t) { builder->dx * scale, builder->dy * 
scale});
+      t = gsk_transform_translate (gsk_transform_ref (cur->transform),
+                                   &(graphene_point_t) { builder->dx * scale, builder->dy * scale});
       t = gsk_transform_transform (t, transform);
       entry->transform = t;