Replace invalid UTF-8 chars when decoding

[cag]

Description

Currently bad UTF-8 sequences cause getPastEvents to crash unrecoverably. Fixing the utility will allow programs to not die while listening to events that have bad logs.

Fixes #1610

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 have executed npm run test:cov and my test cases do cover all lines and branches of the added code.
• I ran npm run build-all and tested the resulting file/'s from dist folder in a browser.
• I have updated the CHANGELOG.md file in the root folder.
• I have tested my code on the live network.

[holgerd77]

Hi @cag, thanks for submitting this PR! Sorry, but for security reasons we just can't depend this library on a library fork which just has been created a couple of days ago.

Will close for now.