Fix parsing of non-eth_subscription provider events

[ryanio]

Description

This PR fixes parsing of non-eth_subscription provider events, such as the new wallet_accountsChanged found in #3659, by adding some additional guards when checking for a subscription callback.

Fixes #3659

Type of change

• Bug fix (non-breaking change which fixes an issue)

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 new warnings.
• Any dependent changes have been merged and published in downstream modules.
• I ran npm run dtslint with success and extended the tests and types if necessary.
• I ran npm run test:unit with success.
• I ran npm run test:cov and my test cases cover all the lines and branches of the added code.
• I ran npm run build and tested dist/web3.min.js in a browser.
• I have tested my code on the live network.
• I have checked the Deploy Preview and it looks correct.
• I have updated the CHANGELOG.md file in the root folder.

[coveralls]

Coverage remained the same at 84.321% when pulling 181cc1f on fix-provider-events into bf06daa on 1.x.

[GregTheGreek]

This is a duplicate of #3642, but this will supersedes that pr since I haven't heard back from the original contributor. At the time I don't think my metamask was updated.

This also closes #3651

need to update changelog

[spacesailor24]

Changelog was updated, and after testing changes locally, I no longer receive an error when changing accounts in Metamask

[JF0001]

Hi,
I am on Metamask Version 8.0.5, but I am still obtaining this error when using window.ethereum.on(accountsChanged, callbackFunction): Uncaught TypeError: Cannot read property 'subscription' of undefined
Furthermore, please note that contrary to DotCoyote who has reported the issue, my CallBack Function is not executing properly, as it used to.
Was this fixed? Where can I obtain the patch?
Thank you. J

[GregTheGreek]

@JF0001 This currently exists on the 1.x branch, it has not yet been published. can you test that version out ?

[JF0001]

Thank you Gregory. Yes, I am no longer seeing the error. The account change in MetaMask is not properly triggering the method, but that is most likely due to my code, which I have been modifying extensively. Could you please add a note to this thread if possible if anything else is modified regarding this fix.
Thank you again. J