scour: Fix another variant of the crash from #260 (#264)

Signed-off-by: Niels Thykier <niels@thykier.net>

scour/scour.py

@@ -1200,11 +1200,11 @@ def mergeSiblingGroupsWithCommonAttributes(elem):
         for node in nodes:
             if node.nodeType == Node.ELEMENT_NODE and node.nodeName == 'g' and node.namespaceURI == NS['SVG']:
                 # Merge
-                primaryGroup.childNodes.extend(node.childNodes)
-                node.childNodes = []
+                for child in node.childNodes[:]:
+                    primaryGroup.appendChild(child)
+                elem.removeChild(node).unlink()
             else:
-                primaryGroup.childNodes.append(node)
-            elem.childNodes.remove(node)
+                primaryGroup.appendChild(node)
 
     # each child gets the same treatment, recursively
     for childNode in elem.childNodes:

test_scour.py

@@ -2099,6 +2099,12 @@ class GroupSiblingMerge(unittest.TestCase):
         self.assertEqual(doc.getElementsByTagName('g').length, 8,
                          'Sibling merging is disabled by --disable-group-collapsing')
 
+    def test_sibling_merge_crash(self):
+        doc = scourXmlFile('unittests/group-sibling-merge-crash.svg',
+                           parse_args(['']))
+        self.assertEqual(doc.getElementsByTagName('g').length, 1,
+                         'Sibling merge should work without causing crashes')
+
 
 class GroupCreation(unittest.TestCase):
 

unittests/group-sibling-merge-crash.svg

@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<svg version="1.1" id="Layer_1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" x="0" y="0" viewBox="0 0 141.732 141.732" xml:space="preserve">
+  <g>
+    <g clip-path="url(#SVGID_2_)">
+      <path d="M1,1" fill="#fdebc8" stroke="#000" stroke-width=".5" stroke-miterlimit="10"/>
+    </g>
+    <g clip-path="url(#SVGID_2_)">
+      <g>
+        <path opacity=".5" clip-path="url(#SVGID_4_)" fill="#fff" d="M1,1"/>
+      </g>
+    </g>
+  </g>
+</svg>