Fix Comparsion Operation to Strict Equal

[kazikai]

The "==" or "!=" operator is not strict comparison operator.
It means equality without type coercion.
so we should be avoided.

[kazikai]

Hi, Recently I commit to Handlebars Github Proejct
But. my commit is failed in CI Build. Why do I build fails?
Thank You,

[stevenvachon]

Try changing the === null back to == null as this will catch both null and undefined.

[kazikai]

Thank You, your response!: I understand it

[nknapp]

The failing test seems to be related to PR #1180 and not this one.