0.2.1 defaultProps migration introduces breaking change

[mmaloon]

Describe the bug
Release 0.2.1 introduces bug where explicitly passing undefined as a className causes an error

Reproducible test case
Codepen Demo

Expected behavior
This has potential to break existing code. Maybe revert and save for a major release?

This code works for version 0.2.0 but not on 0.2.1
<FontAwesomeIcon className={undefined} icon={faUser} />

[mmaloon]

Didn't realize there is already a pull-request discussing this issue: #559

[shehi]

Regardless of any PRs, this issue should exist.

The usage of .split() function contradicts TS typing of className props which is nullable:

[robmadole]

Thanks, I'll take a look at this.

[robmadole]

Just released 0.2.2. Please give this a try.