SVGFontFaceElement::removedFrom should not use FontSelector when document is not active.

Source/core/svg/SVGFontFaceElement.cpp

 /*
  * Copyright (C) 2007 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2007, 2008 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2008 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 317 matching lines @@
     return InsertionDone;
 }
 
 void SVGFontFaceElement::removedFrom(ContainerNode* rootParent)
 {
     SVGElement::removedFrom(rootParent);
 
     if (rootParent->inDocument()) {
         m_fontElement = 0;
         document().accessSVGExtensions().unregisterSVGFontFaceElement(this);
-        document().styleEngine()->fontSelector()->fontFaceCache()->remove(m_fontFaceRule.get());
+        // FIXME: HTMLTemplateElement's document or imported  document can be active?
+        // If so, we also need to check whether fontSelector() is nullptr or not.
+        // Otherwise, we will use just document().isActive() here.
+        if (document().isActive() && document().styleEngine()->fontSelector())
+            document().styleEngine()->fontSelector()->fontFaceCache()->remove(m_fontFaceRule.get());
         m_fontFaceRule->mutableProperties().clear();
 
         document().styleResolverChanged(RecalcStyleDeferred);
     } else
         ASSERT(!m_fontElement);
 }
 
 void SVGFontFaceElement::childrenChanged(bool changedByParser, Node* beforeChange, Node* afterChange, int childCountDelta)
 {
     SVGElement::childrenChanged(changedByParser, beforeChange, afterChange, childCountDelta);
     rebuildFontFace();
 }
 
 } // namespace WebCore
 
 #endif // ENABLE(SVG_FONTS)