PVS-Studio warning V595 for Xerces

DOMComment *DOMCommentImpl::splitText(XMLSize_t offset)
{
  ....
  DOMDocumentImpl *doc = (DOMDocumentImpl *)getOwnerDocument();

  DOMComment *newText =
    doc->createComment(
      this->substringData(offset, len - offset));
  ....
  if (doc != 0) {
  ....
}

This suspicious code was found in Xerces project by PVS-Studio static code analyzer.
Warning message is:
V595 The 'doc' pointer was utilized before it was verified against nullptr. Check lines: 106, 114. domcommentimpl.cpp 106

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