Check for null selectors when looping in findBestRuleSetAndAdd

Source/core/css/CSSSelector.cpp

Index: Source/core/css/CSSSelector.cpp
diff --git a/Source/core/css/CSSSelector.cpp b/Source/core/css/CSSSelector.cpp
index cddc68bff4e022860b91c4ebc77f4e2d83d71c1e..94238d4c17481b5b12a844c5c404e252577c8dc6 100644
--- a/Source/core/css/CSSSelector.cpp
+++ b/Source/core/css/CSSSelector.cpp
@@ -397,6 +397,8 @@ void CSSSelector::show(int indent) const
     if (tagHistory()) {
         printf("\n%*s--> (relation == %d)\n", indent, "", relation());
         tagHistory()->show(indent + 2);
+    } else {
+        printf("\n%*s--> (relation == %d)\n", indent, "", relation());
     }
 }