Fix notice non-object on $parentOfTopCandidate for tumblr.com

PHP notice on DOMElement $parentOfTopCandidate.
  Trying to get property of non-object in serc/Readability.php line 1000
  Trying to get property of non-object in serc/Readability.php line 1009

Reproduced with this url:
  https://clipartx.tumblr.com/post/172752750628/orange-swirl-burnt-orange-orange

Config:
  $config = new Configuration;
  $config->setWordThreshold(5)
    ->setSummonCthulhu(true)
    ->setFixRelativeURLs(true)
    ->setOriginalURL($url);

1 files changed, 5 insertions, 2 deletions

diff --git a/src/Readability.php b/src/Readability.php
index 93fc810..2623bb2 100644
--- a/src/Readability.php
+++ b/src/Readability.php
@@ -997,7 +997,7 @@ class Readability
             $MINIMUM_TOPCANDIDATES = 3;
             if (count($alternativeCandidateAncestors) >= $MINIMUM_TOPCANDIDATES) {
                 $parentOfTopCandidate = $topCandidate->parentNode;
-                while ($parentOfTopCandidate->nodeName !== 'body') {
+                while ($parentOfTopCandidate->nodeName !== 'body' && $parentOfTopCandidate->nodeType === XML_ELEMENT_NODE) {
                     $listsContainingThisAncestor = 0;
                     for ($ancestorIndex = 0; $ancestorIndex < count($alternativeCandidateAncestors) && $listsContainingThisAncestor < $MINIMUM_TOPCANDIDATES; $ancestorIndex++) {
                         $listsContainingThisAncestor += (int)in_array($parentOfTopCandidate, $alternativeCandidateAncestors[$ancestorIndex]);
@@ -1047,7 +1047,10 @@ class Readability
             // If the top candidate is the only child, use parent instead. This will help sibling
             // joining logic when adjacent content is actually located in parent's sibling node.
             $parentOfTopCandidate = $topCandidate->parentNode;
-            while ($parentOfTopCandidate->nodeName !== 'body' && count($parentOfTopCandidate->getChildren(true)) === 1) {
+            while ($parentOfTopCandidate->nodeName !== 'body'
+                   && $parentOfTopCandidate->nodeType === XML_ELEMENT_NODE
+                   && count($parentOfTopCandidate->getChildren(true)) === 1
+            ) {
                 $topCandidate = $parentOfTopCandidate;
                 $parentOfTopCandidate = $topCandidate->parentNode;
             }