AdditionalProperties not being applied when value could be array

[dharanikumar-19]

This fix should will resolve this issue #404

Given the following schema:

{ "type": [ "object", "null" ], "properties": { "a_string": { "type": "string" } }, "additionalProperties": false }
The sample data
object = { "a_string": "this property is allowed by the schema", "an_extra_string": "the schema does not allow this property" }

Previously it does not raise any error

After the fix
Following error will throw
JSON::Schema::ValidationError: The property '#/' contains additional properties ["an_array"] outside of the schema when none are allowed

[pboling]

#423 (comment)

[bastelfreak]

Hi @dharanikumar-19, thanks for this PR. Are you able to rebase and add tests for the change?