fix(plugin-legacy): empty base makes import fail (fixes #4212)

[sapphi-red]

Description

fixes #4212

I tested with Chrome 53.

Additional context

Maybe '' could be replaced to './' in resolveConfig instead?

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What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

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[patak-dev]

Maybe '' could be replaced to './' in resolveConfig instead?

Yes, this is an option. We'll need to discuss with the team if we want to deprecate both '' and './' in favor of 'auto', or if we decide for '' or './' and deprecate with a warning or an error in v3 the other one. I would prefer to have a single option, and lately, I'm leaning towards '', false, or null. I think the relative base not being a string is better to avoid future errors as it will force us to always check the base type.

[sapphi-red]

I'm in favor of having a single option. null could be confusing with omitting the value. So I think false is better if we are going to using a type other than string.