[librsvg/librsvg-2.44] Handle child being in error in feMerge

[Federico Mena Quintero <federico src gnome org>]

commit 80f62dfaeb0c0a5c8b110b8ebee44d0720c3bee8
Author: Ivan Molodetskikh <yalterz gmail com>
Date:   Tue Sep 25 11:37:48 2018 +0300

    Handle child being in error in feMerge

 rsvg_internals/src/filters/merge.rs | 4 ++++
 1 file changed, 4 insertions(+)
---
diff --git a/rsvg_internals/src/filters/merge.rs b/rsvg_internals/src/filters/merge.rs
index a2799d33..08668c7c 100644
--- a/rsvg_internals/src/filters/merge.rs
+++ b/rsvg_internals/src/filters/merge.rs
@@ -142,6 +142,10 @@ impl Filter for Merge {
             .children()
             .filter(|c| c.get_type() == NodeType::FilterPrimitiveMergeNode)
         {
+            if child.is_in_error() {
+                return Err(FilterError::ChildNodeInError);
+            }
+
             bounds = bounds.add_input(
                 &child
                     .with_impl(|c: &MergeNode| ctx.get_input(draw_ctx, c.in_.borrow().as_ref()))?,