Assert fail -- contents array shorter than expected

Seen in fbf9dd33aec2a206238cea13397afc46bc7fe5faba4d136a9998ce8e084d7eee

/Contents is a ref to 17 0 obj, where the array contains a ref to object 18, which is a stream containing the contents. parse_pagenode attempts to H_INDEX() field 1 of the contents array (HCountedArray holding single Ref token to object 18), and fails.