Adjust error-handling for invalid filter primitive references

Source/core/svg/graphics/filters/SVGFilterBuilder.cpp

 /*
  * Copyright (C) 2009 Dirk Schulze <krit@webkit.org>
  *
  * 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.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 30 matching lines @@
 
     if (m_builtinEffects.contains(id))
         return;
 
     m_lastEffect = effect;
     m_namedEffects.set(id, m_lastEffect);
 }
 
 FilterEffect* SVGFilterBuilder::getEffectById(const AtomicString& id) const
 {
-    if (id.isEmpty()) {
-        if (m_lastEffect)
-            return m_lastEffect.get();
+    if (!id.isEmpty()) {
+        if (FilterEffect* builtinEffect = m_builtinEffects.get(id))
+            return builtinEffect;
 
-        return m_builtinEffects.get(SourceGraphic::effectName());
+        if (FilterEffect* namedEffect = m_namedEffects.get(id))
+            return namedEffect;
     }
 
-    if (m_builtinEffects.contains(id))
-        return m_builtinEffects.get(id);
+    if (m_lastEffect)
+        return m_lastEffect.get();
 
-    return m_namedEffects.get(id);
+    return m_builtinEffects.get(SourceGraphic::effectName());
 }
 
 void SVGFilterBuilder::appendEffectToEffectReferences(PassRefPtr<FilterEffect> prpEffect, RenderObject* object)
 {
     RefPtr<FilterEffect> effect = prpEffect;
 
     // The effect must be a newly created filter effect.
     ASSERT(!m_effectReferences.contains(effect));
     ASSERT(object && !m_effectRenderer.contains(object));
     m_effectReferences.add(effect, FilterEffectSet());
@@ skipping 22 matching lines @@
 
     effect->clearResult();
 
     HashSet<FilterEffect*>& effectReferences = this->effectReferences(effect);
     HashSet<FilterEffect*>::iterator end = effectReferences.end();
     for (HashSet<FilterEffect*>::iterator it = effectReferences.begin(); it != end; ++it)
          clearResultsRecursive(*it);
 }
 
 } // namespace blink