Make Element::attributes() less error-prone and simplify call sites

Source/core/html/parser/HTMLConstructionSite.cpp

Index: Source/core/html/parser/HTMLConstructionSite.cpp
diff --git a/Source/core/html/parser/HTMLConstructionSite.cpp b/Source/core/html/parser/HTMLConstructionSite.cpp
index e4f8b819a5d71fbef238d5a0f22852f99f2d7565..7c6b27a2cd0da23c5f0bb6ddc259843009996441 100644
--- a/Source/core/html/parser/HTMLConstructionSite.cpp
+++ b/Source/core/html/parser/HTMLConstructionSite.cpp
@@ -407,7 +407,7 @@ void HTMLConstructionSite::mergeAttributesFromTokenIntoElement(AtomicHTMLToken*
 
     for (unsigned i = 0; i < token->attributes().size(); ++i) {
         const Attribute& tokenAttribute = token->attributes().at(i);
-        if (!element->elementData() || element->attributes().findIndex(tokenAttribute.name()) == kNotFound)
+        if (element->attributesWithoutUpdate().findIndex(tokenAttribute.name()) == kNotFound)
             element->setAttribute(tokenAttribute.name(), tokenAttribute.value());
     }
 }