Add NULL check for renderBox::layer() on applying zoom level change

Source/core/rendering/RenderBox.cpp

Index: Source/core/rendering/RenderBox.cpp
diff --git a/Source/core/rendering/RenderBox.cpp b/Source/core/rendering/RenderBox.cpp
index a7c43665778a45f7fbb1e35fa5dbf0fa0c34c493..38053d64fe357e8aad0fdd371eea783da637e566 100644
--- a/Source/core/rendering/RenderBox.cpp
+++ b/Source/core/rendering/RenderBox.cpp
@@ -254,7 +254,7 @@ void RenderBox::styleDidChange(StyleDifference diff, const RenderStyle* oldStyle
 
     // If our zoom factor changes and we have a defined scrollLeft/Top, we need to adjust that value into the
     // new zoomed coordinate space.
-    if (hasOverflowClip() && oldStyle && newStyle && oldStyle->effectiveZoom() != newStyle->effectiveZoom()) {
+    if (hasOverflowClip() && oldStyle && newStyle && oldStyle->effectiveZoom() != newStyle->effectiveZoom() && layer()) {
         if (int left = layer()->scrollXOffset()) {
             left = (left / oldStyle->effectiveZoom()) * newStyle->effectiveZoom();
             layer()->scrollToXOffset(left);