Empty line before comment should (sometimes) be preserved

[bbannier]

Currently zeek-format removes empty lines before any minor comments, e.g.,

event new_event(name: string, params: call_argument_vector)
	{
	print name;
	}

# Should preserve empty line before.

first gets formatted to

event new_event(name: string, params: call_argument_vector)
	{
	print name;
	}

	# Should preserve empty line.

and then again (breaking idempotency) to

event new_event(name: string, params: call_argument_vector)
	{
	print name;
	}
	# Should preserve empty line.

I would have expect this to not change formatting at all.

zeek-format should still remove empty after e.g., { (comment first node in block).

Labelling as bug due to idempotency breaking.