Symfony version(s) affected: 4.2.4

Description
Yaml component can't parse simple JSON. JSON is valid Yaml.

How to reproduce

\Symfony\Component\Yaml\Yaml::parse("{\n \n}");

Additional context
I believe this has to do with bad whitespace assumptions.

Error message is

Uncaught Symfony\Component\Yaml\Exception\ParseException: Unable to parse at line 1 (near "{").