firstOrDefault default value that equates to false yields null

[Bob Vale]

If you call firstOrDefault with a default value that equates to false then the return value will be null if the enumerable is empty.

testing.firstOrDefault(null, 0) yields null
testing.firstOrDefault(null, false) yiels null

This is because line at 1869 defaultValue = defaultValue || null

shouldn't it be defaultValue = (typeof(defaultValue) === 'undefined') ? null : defaultValue

That way passing in null yields null, passing in an undefined value yields null everything else yields the supplied defaultValue when the enumerable is empty

[Bob Vale]

also elementAtOrDefault and lastOrDefault suffer the same issue.