ReflectionParameter::hasType() should assert return type of ReflectionParameter::getType()

If `ReflectionParameter::hasType()` returns `true`, then `ReflectionParameter::getType()` will always return `ReflectionType`.

If `ReflectionParameter::hasType()` returns `false`, then `ReflectionParameter::getType()` will always return `null`.

This is not currently understood by psalm.

https://psalm.dev/r/257f4e884d