CSV export is broken for tables with null foreign keys

[simonw]

Following on from #406 - this CSV export appears to be broken:

https://14da705.datasette.io/fixtures/foreign_key_references.csv?_labels=on&_size=max

pk,foreign_key_with_label,foreign_key_with_label_label,foreign_key_with_no_label,foreign_key_with_no_label_label
1,1,hello,1,1
2,,

That second row should have 5 values, but it only has 4.

[simonw]

The bug is in this code here:

datasette/datasette/views/base.py

Lines 331 to 338 in c3181d9

	# Look for {"value": "label": } dicts and expand
	new_row = []
	for cell in row:
	if isinstance(cell, dict):
	new_row.append(cell["value"])
	new_row.append(cell["label"])
	else:
	new_row.append(cell)

[simonw]

This is a blocker on releasing 0.30.2