Swizzling an empty list throws exception instead of returning zero-width value

[mkorbel1]

Describe the bug

Swizzling an empty list causes an "invalid radix-2 number" type of exception to get thrown since down the line there is a blank string passed to int.parse.

To Reproduce

<LogicValues>[].swizzle()

Expected behavior

An empty list should return a zero-width value.

Actual behavior

An exception related to the underlying implementation of swizzle is thrown, confusing users.