The index-of-pred function used (nil? c) to detect end-of-collection,
which caused premature termination when the collection contained nil
values. Rewrite using (seq coll) / (next s) pattern to correctly
distinguish between nil elements and end-of-sequence.
The deep-mapm function was applying the mapping function twice on
leaf entries (non-map, non-vector values): once when destructuring
the entry, and again on the already-transformed result in the else
branch. Now mfn is applied exactly once per entry.
The patch-object function was calling (dissoc object key value) when
handling nil values. Since dissoc treats each argument after the map
as a key to remove, this was also removing nil as a key from the map.
The correct call is (dissoc object key).
