History::SetFiles check #1778

[atishhamte]

History::SetFiles check #1778

As per the issue raised, In case one of the files in WRITEPATH.'debugger/debugbar_*.json is empty the method setFiles will crash. The reason for the crash is that History::setFiles does not check if the local variable $contents contain an object before using it in the assignment.

I have added a check whether the JSON is valid or not. If not then it will skip the iteration else proceed with it.

Checklist:

• Securely signed commits
• Component(s) with PHPdocs
• Unit testing, with >80% coverage
• User guide updated
• Conforms to style guide

[atishhamte]

Travis ci failed only in PHP 7.2, MySQL but passed in all other scenario.
@lonnieezell @jim-parry could you please check as I have changed nothing related to redis