From f0edc6efd725aaf654bf1acbfc487d948941f191 Mon Sep 17 00:00:00 2001
From: Guillaume Ayoub <guillaume@courtbouillon.org>
Date: Fri, 11 Dec 2020 22:39:56 +0100
Subject: [PATCH] =?UTF-8?q?Don=E2=80=99t=20crash=20when=20use=20tags=20ref?=
 =?UTF-8?q?erence=20unknown=20tags?=
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Fix #303.
---
 cairosvg/defs.py | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/cairosvg/defs.py b/cairosvg/defs.py
index f65bbeeb..98533270 100644
--- a/cairosvg/defs.py
+++ b/cairosvg/defs.py
@@ -346,9 +346,13 @@ def use(surface, node):
     if 'mask' in node:
         del node['mask']
     href = parse_url(node.get_href()).geturl()
-    tree = Tree(
-        url=href, url_fetcher=node.url_fetcher, parent=node,
-        tree_cache=surface.tree_cache, unsafe=node.unsafe)
+    try:
+        tree = Tree(
+            url=href, url_fetcher=node.url_fetcher, parent=node,
+            tree_cache=surface.tree_cache, unsafe=node.unsafe)
+    except TypeError:
+        surface.context.restore()
+        return
 
     if not match_features(tree.xml_tree):
         surface.context.restore()