Auditable trait. Failed resolveUserAgent when User-Agent is empty

[dominikveils]

Q	A
Bug?	yes
New Feature?	yes
Framework	Laravel
Framework version	5.5
Package version	v5.0.3
PHP version	7.x.y

Actual Behaviour

PHP7 type error (return value) is thrown when request missing User-Agent header.

Expected Behaviour

Expected to get empty User-Agent, not null or exception

Steps to Reproduce

Make http request without User-Agent header and save Auditable model.

Possible Solutions

Explicity typecast to (string) return value of resolveUserAgent and other functions in Auditable trait.

[quetzyg]

Thanks for reporting this @dominikveils, I'll fix it ASAP.

[quetzyg]

In version 6, the default User Agent resolver won't have this issue.

[quetzyg]

While version 6 isn't released, I've tagged version 5.0.4, which addresses this problem.