2 files changed, 13 insertions, 4 deletions
diff --git a/WebCore/mathml/RenderMathMLRoot.cpp b/WebCore/mathml/RenderMathMLRoot.cpp
index 4ed8c19..da303c9 100644
--- a/WebCore/mathml/RenderMathMLRoot.cpp
+++ b/WebCore/mathml/RenderMathMLRoot.cpp
@@ -99,7 +99,10 @@ void RenderMathMLRoot::paint(PaintInfo& info, int tx, int ty)
     
     if (info.context->paintingDisabled())
         return;
-    
+
+    if (!firstChild() || !lastChild())
+        return;
+
     tx += x();
     ty += y();
     
@@ -203,11 +206,15 @@ void RenderMathMLRoot::paint(PaintInfo& info, int tx, int ty)
 void RenderMathMLRoot::layout()
 {
     RenderBlock::layout();
-    
+
+    if (!firstChild() || !lastChild())
+        return;
+
     int maxHeight = toRenderBoxModelObject(lastChild())->offsetHeight();
     
     RenderObject* current = lastChild()->firstChild();
-    current->style()->setVerticalAlign(BASELINE);
+    if (current)
+        current->style()->setVerticalAlign(BASELINE);
     
     if (!maxHeight)
         maxHeight = style()->fontSize();
@@ -228,6 +235,8 @@ void RenderMathMLRoot::layout()
     
     // Positioning of the index
     RenderBoxModelObject* indexBox = toRenderBoxModelObject(firstChild()->firstChild());
+    if (!indexBox)
+        return;
     
     int indexShift = indexBox->offsetWidth() + topStartShift;
     int radicalHeight = static_cast<int>((1 - gRadicalTopLeftPointYPos) * maxHeight);
diff --git a/WebCore/mathml/RenderMathMLSubSup.cpp b/WebCore/mathml/RenderMathMLSubSup.cpp
index 52ac0e3..4cda36f 100644
--- a/WebCore/mathml/RenderMathMLSubSup.cpp
+++ b/WebCore/mathml/RenderMathMLSubSup.cpp
@@ -162,7 +162,7 @@ void RenderMathMLSubSup::layout()
                     maxHeight = height;
                 current = current->nextSibling();
             }
-            int heightDiff = (m_scripts->offsetHeight() - maxHeight) / 2;
+            int heightDiff = m_scripts ? (m_scripts->offsetHeight() - maxHeight) / 2 : 0;
             if (heightDiff < 0) 
                 heightDiff = 0;
             base->style()->setMarginTop(Length(heightDiff, Fixed));