[cairo] Segfault at sweep_line_delete on video playback

[James Cloos]

This diff avoids the segfault for me, but only papers over the bug...

diff --git a/src/cairo-bentley-ottmann-rectangular.c b/src/cairo-bentley-ottmann-rectangular.c
index 5541bdc..c3607cf 100644
--- a/src/cairo-bentley-ottmann-rectangular.c
+++ b/src/cairo-bentley-ottmann-rectangular.c
@@ -564,7 +564,9 @@ sweep_line_delete (sweep_line_t	*sweep, rectangle_t *rectangle)
     cairo_bool_t update;
 
     update = TRUE;
+    
     if (sweep->fill_rule == CAIRO_FILL_RULE_WINDING &&
+	rectangle->left.prev &&
 	rectangle->left.prev->dir == rectangle->left.dir)
     {
 	update = rectangle->left.next != &rectangle->right;
diff --git a/src/cairo-clip.c b/src/cairo-clip.c
index 0df9b06..736838f 100644
--- a/src/cairo-clip.c
+++ b/src/cairo-clip.c
@@ -88,7 +88,11 @@ _cairo_clip_path_reference (cairo_clip_path_t *clip_path)
 void
 _cairo_clip_path_destroy (cairo_clip_path_t *clip_path)
 {
+    /*
     assert (CAIRO_REFERENCE_COUNT_HAS_REFERENCE (&clip_path->ref_count));
+    */
+    if (!clip_path)
+	return;
 
     if (! _cairo_reference_count_dec_and_test (&clip_path->ref_count))
 	return;