Cherry-pick 3113660. rdar://122892811

    Null pointer dereference in elementHasClassInClosestAncestors
    https://bugs.webkit.org/show_bug.cgi?id=269308
    rdar://122892811

    Reviewed by Brent Fulgham.

    Ensure ancestor is non-null before accessing it.

    * Source/WebCore/page/Quirks.cpp:
    (WebCore::elementHasClassInClosestAncestors):

    Canonical link: https://commits.webkit.org/274575@main

Canonical link: https://commits.webkit.org/272448.566@safari-7618.1.15.10-branch

Source/WebCore/page/Quirks.cpp

@@ -1152,17 +1152,14 @@ static bool elementHasClassInClosestAncestors(const Element& element, const Atom
     if (element.hasClass() && element.classNames().contains(className))
         return true;
 
-    unsigned currentDistance = 1;
+    unsigned currentDistance = 0;
     RefPtr ancestor = dynamicDowncast<Element>(element.parentNode());
-    while (currentDistance <= distance) {
+    while (ancestor && currentDistance < distance) {
+        ++currentDistance;
         if (ancestor->hasClass() && ancestor->classNames().contains(className))
             return true;
 
         ancestor = dynamicDowncast<Element>(ancestor->parentNode());
-        if (!ancestor)
-            return false;
-
-        ++currentDistance;
     }
     return false;
 }