Here are two questions:
Q1 was marked as a duplicate and merged with Q2. Q2 has since been deleted, leaving Q1 dangling - it is accessible, but cannot be answered. This kind of dead-end question (no answer, not allowed to answer, no referral) doesn't really have a place on Q&A sites such as ELU.
Now, since Q2 was deleted, presumably it was a low-quality question or unsuitable for ELU for some other reason (I have no information on that). The fact that Q1 was merged into Q2 suggests that Q1 was of lower quality than Q2 or otherwise even more unsuitable than Q2 for ELU. As such, when questions like Q2 are deleted, should questions such as Q1 that have been merged into them also automatically be deleted? Alternatively, should merged questions like Q1 be individually reviewed when questions like Q2 are deleted?
Are there any mechanisms for easily finding merged-in questions when deleting a question? That is, when deleting questions like Q2, does a list pop up to show dependent questions like Q1? If not, consider this a feature-request for such a mechanism.