Calling new Web3() without a provider.

[nivida]

Description

Fixes #2689

Type of change

• Bug fix

Checklist:

• I have selected the correct base branch.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation.
• My changes generate no warnings.
• I have updated or added types for all modules I've changed
• Any dependent changes have been merged and published in downstream modules.
• I ran npm run test in the root folder with success and extended the tests if necessary.
• I ran npm run build in the root folder and tested it in the browser and with node.
• I ran npm run dtslint in the root folder and tested that all my types are correct
• I have tested my code on an ethereum test network.

[joshstevens19]

Don't forget to update the typing's here 👍 https://github.com/ethereum/web3.js/blob/1.0/packages/web3/types/index.d.ts#L32

[coveralls]

Coverage increased (+0.003%) to 95.548% when pulling b5410bc on issue/2689 into b18a1eb on 1.0.