Raise UnsupportedFormat for a non-dict row in a list of records

[eeshsaxena]

When the dict setter (used by JSON and YAML import) gets a list whose first item is a dict but which also contains a non-dict item, it calls row.values() on that item and raises a bare AttributeError. A YAML document like - a: 1/- null or JSON [{"a": 1}, null] triggers it. I check each row is a dict and raise UnsupportedFormat instead, matching what the setter already raises for other malformed input.

[eeshsaxena]

Hi! Gentle nudge on this one whenever you have some bandwidth. It's a small, self-contained fix (Raise UnsupportedFormat for a non-dict row in a list of records), and it's currently mergeable with no conflicts. No urgency at all, and I'm happy to make any changes you'd like. Thanks for maintaining tablib!