Fix array<empty, empty> not in array{foo?: mixed}<string, mixed>

[VincentLanglet]

Trying to fix #4963
I tried to modify my vendor and this seems to fix the issue but there is certainly some improvements.

I'm not familiar at all with the different types.
Should I do something with List too ? Is there an easier way to check for empty array ?

[VincentLanglet]

I can't decide if I should create a new file for the test or add one to an existing file ; any thought @muglug ?

[muglug]

Merge/rebase master, where you'll find a tests/TypeComparatorTest.php with a place to slot yours in.

[VincentLanglet]

Thanks @muglug, it works well. Test are failing without my fix. It's ready to be reviewed/improved :)

[muglug]

Thanks!